From: dvansomm@mars.ocs.mq.edu.au Date: Wed, 21 Oct 1998 12:05:05 +1000 (EST) Dear Professor Hudson, Here are your 88 citations. Congratulations! Di van Sommers ---------- Forwarded message ---------- Date: Wed, 21 Oct 1998 11:55:34 +1000 (EST) From: dvansomm@mars.ocs.mq.edu.au To: dvansomm@mars.ocs.mq.edu.au File 34:SciSearch(R) Cited Ref Sci 1990-1998/Oct W2 (c) 1998 Inst for Sci Info Set Items Description --- ----- ----------- ?e cr=hudson hm, 1993? Ref Items Index-term E1 2 CR=HUDSON HM, 1992, V58, P784, AM SURGEON E2 3 CR=HUDSON HM, 1992, V6, P193, SURG ENDOSC-ULTRAS E3 0 *CR=HUDSON HM, 1993? E4 1 CR=HUDSON HM, 1994, IN PRESS IEEE T MED E5 1 CR=HUDSON HM, 1994, V12, P601, IEEE T MED IMAGING E6 85 CR=HUDSON HM, 1994, V13, P601, IEEE T MED IMAGING E7 1 CR=HUDSON HM, 1994, V13, P61, IEEE T MED IMAGING E8 1 CR=HUDSON HM, 1994, V20, P100, IEEE T MED IMAGING E9 1 CR=HUDSON HM, 1994, V3, P41, STAT METHOD MED RES E10 3 CR=HUDSON HM, 1994, V3, P41, STAT METHODS MED RES E11 1 CR=HUDSON HM, 1994, V3, P87, STAT METHODS MED RES E12 1 CR=HUDSON HM, 1994, V3, P87, STATISTICAL METHODS Enter P or PAGE for more ?s e4:e7 S1 88 CR="HUDSON HM, 1994, IN PRESS IEEE T MED":CR="HUDSON HM, 1994, V13, P61, IEEE T MED IMAGING" ?t s1/7/all 1/7/1 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 07018292 Genuine Article#: 115PY Number of References: 472 Title: Highlights of statistical signal and array processing Author(s): Chen TH (REPRINT) ; Hero A; Djuric PM; Messer H; Goldberg J; Thomson DJ; Amin MG; Krim H; Pesquet JC; Giannakis G; Swami A; Tugnait JK; Cardoso JF; Tong L; Krolik J Corporate Source: CARNEGIE MELLON UNIV,/PITTSBURGH//PA/15213 (REPRINT); UNIV MICHIGAN,/ANN ARBOR//MI/48109; UNIV VIRGINIA,/CHARLOTTESVILLE//VA/22903; VILLANOVA UNIV,/VILLANOVA//PA/19085; ECOLE NATL SUPER TELECOMMUN BRETAGNE,/PARIS//FRANCE/; AUBURN UNIV,/AUBURN//AL/36849; SUNY STONY BROOK,/STONY BROOK//NY/11794; N CAROLINA STATE UNIV,/RALEIGH//NC/27695; DUKE UNIV,/DURHAM//NC/27706; PORTLAND STATE UNIV,/PORTLAND//OR/97207; TEL AVIV UNIV,/IL-69978 TEL AVIV//ISRAEL/; UNIV ILLINOIS,/CHICAGO//IL/; UNIV COLORADO,/BOULDER//CO/80309; USA,RES LAB/WASHINGTON//DC/20310; BRIGHAM YOUNG UNIV,/PROVO//UT/84602; ROCHESTER INST TECHNOL,/ROCHESTER//NY/14623; CORNELL UNIV,/ITHACA//NY/14853; CHALMERS UNIV TECHNOL,/S-41296 GOTHENBURG//SWEDEN/; UNIV TEXAS,/AUSTIN//TX/78712 ; PURDUE UNIV,/W LAFAYETTE//IN/47907 Journal: IEEE SIGNAL PROCESSING MAGAZINE, 1998, V15, N5 (SEP), P21-64 ISSN: 1053-5888 Publication date: 19980900 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: REVIEW 1/7/2 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 07014666 Genuine Article#: 115GZ Number of References: 28 Title: Optimized acquisition time and image sampling for dynamic SPECT of Tl-201 Author(s): Lau CH; Eberl S; Feng DG (REPRINT) ; Iida H; Lun PK; Siu WC; Tamura Y; Bautovich GJ; Ono Y Corporate Source: UNIV SYDNEY,DEPT COMP SCI, BIOMED & MULTIMEDIA INFORMAT TECHNOL GRP/SYDNEY/NSW 2006/AUSTRALIA/ (REPRINT); UNIV SYDNEY,DEPT COMP SCI, BIOMED & MULTIMEDIA INFORMAT TECHNOL GRP/SYDNEY/NSW 2006/AUSTRALIA/; HONG KONG POLYTECH UNIV,DEPT ELECT ENGN/HONG KONG//HONG KONG/; ROYAL PRINCE ALFRED HOSP,DEPT PET & NUCL MED/SYDNEY/NSW 2050/AUSTRALIA/; RES INST BRAIN & BLOOD VESSELS,DEPT RADIOL & NUCL MED/AKITA 010//JAPAN/ Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1998, V17, N3 (JUN), P 334-343 ISSN: 0278-0062 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: With the recent development in scatter and attenuation correction algorithms, dynamic single photon emission computerized tomography (SPECT) cain potentially yield physiological parameters, with tracers exhibiting suitable kinetics such as thallium-201 (T1-201). a systematic way is proposed to investigate the minimum data acquisition times and sam;ling requirements for estimating physiological parameters with quantitative dynamic SPECT. Two different sampling schemes were investigated with Monte Carlo simulations: 1) continuous data collection for total study duration ranging from 30-240 min, 2) Continuous data collection for first 10-45 min followed by a delayed study at approximately 3 h, Tissue time activity curves with realistic noise were generated from a mean plasma time activity curve and rate constants (K-1 - k(4)) derived from T1-201 kinetic studies ire 16 dogs, Full dynamic sampling schedules DynSS) were compared to optimum sampling schedules (OSS). We found that OSS can reliably estimate the blood Wow related K-1 and V-d comparable to DynSS. A 30-min continuous collection was sufficient if only K-1 was of interest, A split session schedule of a 30-min dynamic followed by a static study at 3 h allowed reliable estimation of both K-1 and V-d avoiding the need for a prolonged (>60-min) continuous dynamic acquisition, The methodology developed should also be applicable to optimizing sampling schedules for ether SPECT tracers, 1/7/3 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 07014665 Genuine Article#: 115GZ Number of References: 43 Title: Application of reconstruction-based scatter compensation to thallium-201 SPECT: Implementations for reduced reconstructed image noise Author(s): Kadrmas DJ (REPRINT) ; Frey EC; Tsui BMW Corporate Source: UNIV UTAH,DEPT RADIOL, MED IMAGING RES LAB, CAMT, 729 ARAPEEN DR/SALT LAKE CITY//UT/84108 (REPRINT); UNIV N CAROLINA,DEPT BIOMED ENGN/CHAPEL HILL//NC/27599; UNIV N CAROLINA,DEPT RADIOL/CHAPEL HILL//NC/27599 Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1998, V17, N3 (JUN), P 325-333 ISSN: 0278-0062 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Scatter compensation in T1-201 single photon emission computed tomography (SPECT) presents an interesting challenge because of the multiple emission energies and relatively large proportion of scattered photons, In this paper, we present a simulation study investigating reconstructed image noise levels arising from various implementations of iterative reconstruction-based scatter compensation (RBSC) in T1-201 SPECT, A two-stage analysis was used to study single and multiple energy window implementations of reconstruction-based scatter compensation, and RBSC was compared to the upper limits on performance for other approaches to handling scatter. In the first stage, singular value decomposition of the system transfer matrix was used to analyze noise levels in a manner independent of the choice of reconstruction algorithm, providing results valid across a wide range of regularizations, In the second stage, the data were reconstructed using maximum-likelihood expectation-maximization, and the noise properties of the resultant images were analyzed. The best RBSC performance was obtained using multiple energy windows, one for each emission photopeak? and RBSC outperformed the upper limit on subtraction-based compensation methods. Implementing RBSC with the correct choice of energy window acquisition scheme is a promising method for performing scatter compensation for T1-201 SPECT. 1/7/4 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06978727 Genuine Article#: 110VJ Number of References: 22 Title: Count-based quantitation of functional renal volume by SPECT imaging Author(s): King MA (REPRINT) ; Narayanan M; Bohyer C; Licho R; Fung LCT Corporate Source: UNIV MASSACHUSETTS,MED CTR, DEPT NUCL MED, 55 LAKE AVE N/WORCESTER//MA/01655 (REPRINT); UNIV MASSACHUSETTS,MED CTR, DEPT SURG, DIV UROL/WORCESTER//MA/01655 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N4,2 (AUG), P 2189-2194 ISSN: 0018-9499 Publication date: 19980800 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: The quantitation of absolute renal functional volume is of interest because many pathological processes are known to affect the growth and parenchymal volume of kidneys. Unlike thresholding and edge-detection methods, the count-based method of volume quantitation is not highly sensitive to boundary definition. In this investigation, count-based kidney volume quantitation was compared to that of fixed threshold-based estimation with and without including attenuation and scatter compensation in the reconstruction. The Alderson Organ Scanning Phantom kidneys were filled with a Tc-99m solution and placed in the Organ scanning phantom. Inserts shaped like the pelvis region of the kidneys were used to vary kidney volume. Emission imaging of the Tc-99m, and transmission imaging of a Gd-153 line source were performed by a triple-headed SPECT system. Without compensating for attenuation and scatter, the count-based method significantly under-estimated kidney volume. When attenuation and scatter compensation were included, count-based volume quantitation was more accurate than volume estimation with a fixed threshold adapted to the image acquisition and reconstruction strategies employed. 1/7/5 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06978724 Genuine Article#: 110VJ Number of References: 18 Title: Slab-by-slab blurring model for geometric point response correction and attenuation correction using iterative reconstruction algorithms Author(s): Bai CY (REPRINT) ; Zeng GL; Gullberg GT; DiFilippo F; Miller S Corporate Source: UNIV UTAH,DEPT RADIOL/SALT LAKE CITY//UT/84132 (REPRINT); PICKER INT,/CLEVELAND//OH/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N4,2 (AUG), P 2168-2173 ISSN: 0018-9499 Publication date: 19980800 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: The distance-dependent geometric point response of a single photon emission computed tomography (SPECT) system and the attenuation effect of photons passing through the object are modeled in an iterative OS-EM reconstruction algorithm to improve both the resolution and quantitative accuracy of the reconstructed images. A specified number of neighboring vertical slices are grouped into a slab, and an efficient incremental slab-by-slab blurring model is introduced to accelerate the reconstruction. The advantage of the slab-by-slab blurring model over the slice-by-slice model is that the computational time is reduced, while still maintaining the spatial resolution and quantitative accuracy of the reconstructed images. The application of this incremental slab-by-slab blurring model with a slice-by-slice attenuation model to the image reconstruction of phantom, Monte Carlo simulated SPECT data, and patient data shows improved resolution and contrast over the images reconstructed without the corrections. The reconstruction is accelerated by a factor of about 1.4, and the projection/backprojection operation is accelerated by a factor of about 5, using the slab-by-slab convolution implementation with 8 slices in a slab compared with the slice-by-slice convolution implementation. 1/7/6 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06978713 Genuine Article#: 110VJ Number of References: 12 Title: A novel geometry for SPECT imaging associated with the EM-type blind deconvolution method Author(s): Liu YH (REPRINT) ; Rangarajan A; Gagnon D; Therrien M; Sinusas AJ; Wackers FJT; Zubal IG Corporate Source: YALE UNIV,SCH MED, 333 CEDAR ST/NEW HAVEN//CT/06520 (REPRINT); PK MED SYST INC,/LACHINE/PQ H8T 1C4/CANADA/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N4,2 (AUG), P 2095-2101 ISSN: 0018-9499 Publication date: 19980800 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Image quality of single-photon emission computerized tomography (SPECT) is essentially determined by count sensitivity of the detector and geometry of the collimator. We introduce a novel geometry for a dual-head SPECT system, one head equipped with a coded aperture collimator and the other head equipped with a conventional parallel hole collimator, to improve the count sensitivity. Two expectation-maximization blind deconvolution (EMBD) algorithms were derived to improve the image resolution of SPECT projections. The algorithms were evaluated using elliptical cylindrical rod phantom data and hand data. The coded aperture and parallel hole projections were acquired simultaneously using the dual-head imaging system. The acquired coded aperture projections were decoded using the standard uniformly redundant array (URA) technique to yield decoded projections. The projections acquired from the parallel hole collimator head were incorporated into the decoded images in the EMBD restoration process. Using the coded aperture collimator, the count sensitivity was markedly increased as compared to the parallel hole collimator, 17-fold increase for the phantom data and approximately 20-fold for the hand data. Image quality and signal-to-noise ratio of the SPECT projections were significantly improved using the EMBD algorithms. The dual-head SPECT imaging system associated with the EM-type blind deconvolution algorithms may be a preferred system for low-count SPECT imaging. 1/7/7 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06968048 Genuine Article#: 109VJ Number of References: 49 Title: Correction of partial volume effects in myocardial SPECT Author(s): Hutton BF (REPRINT) ; Osiecki A Corporate Source: WESTMEAD HOSP,DEPT MED PHYS/WESTMEAD/NSW 2145/AUSTRALIA/ (REPRINT); WESTMEAD HOSP,DEPT NUCL MED/WESTMEAD/NSW 2145/AUSTRALIA/; WESTMEAD HOSP,DEPT ULTRASOUND/WESTMEAD/NSW 2145/AUSTRALIA/ Journal: JOURNAL OF NUCLEAR CARDIOLOGY, 1998, V5, N4 (JUL-AUG), P402-413 ISSN: 1071-3581 Publication date: 19980700 Publisher: MOSBY-YEAR BOOK INC, 11830 WESTLINE INDUSTRIAL DR, ST LOUIS, MO 63146-3318 Language: English Document Type: ARTICLE Abstract: Background. Marked partial volume effects occur in myocardial single photon emission computed tomographic (SPECT) studies because of limited resolution in imaging the myocardial wail and contractile motion of the heart, kittle work has been undertaken to develop correction techniques for SPECT except for efforts to improve the reconstructed resolution. Our purpose was to examine the extent of the problem and propose a correction method, Methods and Results. A potential correction method, developed initially for positron emission tomography, involved estimation of extravascular density by means of subtracting vascular density derived in a blood pool study from total density derived from a transmission study. provided partial volume errors are the same for transmission and emission data, activity per gram of extravascular tissue can be obtained by means of dividing the perfusion regional data by extravascular density for the same region. Simulations were designed to assess the importance of partial volume errors and the use of extravascular density to correct the errors. Recovery coefficients for the myocardium mere estimated by means of simulation of the beating heart on the basis of published values for ventricular dimensions. Resolution for transmission with a scanning line source system was compared with emission resolution, The effect of spillover on measured partial volume losses was assessed, and a method for matching spillover for emission and extravascular density was demonstrated, Correction for partial volume effects was demonstrated for a phantom with variable wall thickness. Significant variation in recovery coefficient was demonstrated between posterior and septal walls for individual patients independent of heart size, Filtering was necessary to account for the difference in transmission resolution measured in the axial direction, Spillover effects had a significant influence on the measured recovery for small objects; however for a specific reconstruction algorithm and defined region size, correction was implemented to match the spillover effects for emission and extravascular density. Use of extravascular density for correction of partial volume loss, for ordered subsets expectation maximization reconstruction with compensation for resolution, was demonstrated to be accurate to within 10%. Conclusions. The feasibility of correcting partial volume effects with extravascular density was demonstrated. Correction is effective provided care is taken to match both resolution and spillover for emission and extravascular density. 1/7/8 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06966904 Genuine Article#: BL37U Number of References: 23 Title: Supervised diffusion parameter selection for filtering SPECT brain images Author(s): Beekman FJ (REPRINT) ; Slijpen ETP; Niessen WJ Corporate Source: UNIV UTRECHT HOSP,IMAGE SCI INST/UTRECHT//NETHERLANDS/ (REPRINT) , 1997, V1252, P164-175 ISSN: 0302-9743 Publication date: 19970000 Publisher: SPRINGER-VERLAG BERLIN, HEIDELBERGER PLATZ 3, W-1000 BERLIN 33, GERMANYLECTURE NOTES IN COMPUTER SCIENCE Series: LECTURE NOTES IN COMPUTER SCIENCE Language: English Document Type: ARTICLE Abstract: Iterative image reconstruction from noisy data, requires regularization to avoid noise amplification in the reconstructed image at high iteration numbers. This is often accomplished by stopping the iteration process at a relatively low number of iterations or by post filtering the reconstructed image. The aim of this paper is to investigate whether stopping is better than post-filtering, and to determine suitable filter functions for Single Photon Emission Computed Tomography (SPECT). As a study example for finding filter functions for a particular imaging situation, projections of a Tc-99m emitting brain phantom are generated by a SPECT simulator which includes effects of the distance dependent camera response, attenuation, scatter and Poisson noise. Iterative reconstructions are performed using three different camera response models, resp. (i) only attenuation (A), (ii) attenuation and camera response (AD) and (iii) attenuation, camera response and scatter (ADS). Optimal filter parameters for each reconstruction are estimated by parameter selection procedures which minimize image differences between the phantom and the filtered SPECT images. 3D linear diffusion (Gaussian filtering) and 3D nonlinear diffusion (Catte scheme) are used. For the Gaussian filter, the parameters to be optimized are the kernel widths in the transaxial plane and the axial direction. Furthermore, the Gaussian filter function allows the widths to change as a function of the distance to the transaxial axis. The Catte scheme is parameterized by the local smoothing as a function of the image gradient, the spatial resolution at which the gradient is calculated, and the ''time-step''. It has been shown for the Gaussian filter that in the case of ADS the difference between the phantom and the filtered reconstruction in terms of the normalized mean squared error (NMSE) is significantly reduced by optimal (i.e, minimum NMSE) filtering compared to early stopping the iterative reconstruction, and the low NMSE is quite stable at high iteration numbers. In the cases of A, AD and ADS: (i) only a. small additional reduction of the NMSE is accomplished by including also invariance and anisotropy of the filter kernel; (ii) at high iteration numbers, the transaxial width of the kernel gets closer to the axial width; (iii) although some image features are better preserved by Catte, the NMSE is not further reduced compared to Gauss. This is consistent with our findings that the optimum Catte scheme converges to Gaussian blurring. Using accurate image formation models during iterative reconstruction is more important than the choice of the filter function. 1/7/9 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06963576 Genuine Article#: 108FG Number of References: 22 Title: Sources of error in tissue and tumor measurements of 5-[F-18]fluorouracil Author(s): Harte RJ (REPRINT) ; Matthews JC; OReilly SM; Price PM Corporate Source: HAMMERSMITH HOSP,ROYAL POSTGRAD MED SCH, PET ONCOL GRP, MRC, CYCLOTRON UNIT, DU CANE RD/LONDON W12 0NN//ENGLAND/ (REPRINT) Journal: JOURNAL OF NUCLEAR MEDICINE, 1998, V39, N8 (AUG), P1370-1376 ISSN: 0161-5505 Publication date: 19980800 Publisher: SOC NUCLEAR MEDICINE INC, 1850 SAMUEL MORSE DR, RESTON, VA 20190-5316 Language: English Document Type: ARTICLE Abstract: Central to the assessment of variability of pharmacokinetic parameters is knowledge of bias and variability of the measurement technique, preventing observed differences from being ascribed inappropriate significance, This article presents an evaluation of sources of error in the measurement of normal tissue and tumor pharmacokinetics using F-18-labeled 5-fluorouracil (FU) and PET. Methods: A standard approach to data acquisition, processing and analysis was developed using a PET scanner, filtered backprojection reconstruction and region of interest analysis. Fourteen tracer 5-[F-18]FU patient studies and a phantom study were completed, with 4 of the patient studies repeated 1 wk later. These data allowed evaluation of the overall reproducibility of the technique and the components of measurement variability due to tissue sampling. The effect of reconstruction technique and sampling region size on quantification was assessed using phantom data. Results: Al measured radioactivity versus time curves were tissue specific, Week-to-week variability in the area under this curve (representing combined physiological and measurement difference) was -3% to +15% for liver and -9% to -16% for spleen and kidney. Metastasis variability was greatest at -20%, Visual and computer realignment of the second paired study produced similar results. Interobserver effects were small compared to differences between studies. Conclusion: These results confirm the feasibility of using PET as a pharmacokinetic tool for 5-[F-18]FU studies. Although overall experimental error (i.e., random variation in data acquisition, processing and analysis) was low, constraints in data interpretation emerged. 1/7/10 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06926661 Genuine Article#: 103XZ Number of References: 106 Title: Transmission scanning in emission tomography Author(s): Bailey DL (REPRINT) Corporate Source: HAMMERSMITH HOSP,MRC, CYCLOTRON UNIT, DUCANE RD/LONDON W12 0HS//ENGLAND/ (REPRINT) Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1998, V25, N7 (JUL), P 774-787 ISSN: 0340-6997 Publication date: 19980700 Publisher: SPRINGER VERLAG, 175 FIFTH AVE, NEW YORK, NY 10010 Language: English Document Type: REVIEW Abstract: Attenuation correction in single-photon (SPET) and positron emission (PET) tomography is now accepted as a vital component for the production of artefact-free, quantitative data. The most accurate attenuation correction methods are based on measured transmission scans acquired before, during, or after the emission scan. Alternative methods use segmented images, assumed attenuation coefficients or consistency criteria to compensate for photon attenuation in reconstructed. images. This review examines the methods of acquiring transmission scans in both SPET and PET and the manner in which these data are used. While attenuation correction gives an exact correction in PET, as opposed to an approximate one in SPET, the magnitude of the correction factors required in PET is far greater than in SPET. Transmission scans also have a number of other potential applications in emission tomography apart from attenuation correction, such as scatter correction, inter-study spatial co-registration and alignment, and motion detection and correction, The ability to acquire high-quality transmission data in practical clinical protocol is now an essential part of the practice of nuclear medicine. 1/7/11 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06850988 Genuine Article#: ZW687 Number of References: 85 Title: Quantitative assessment of regional myocardial blood flow with thallium-201 and SPECT Author(s): Iida H (REPRINT) ; Eberl S Corporate Source: RES INST BRAIN & BLOOD VESSELS,DEPT RADIOL & NUCL MED, 6-10 SENSHU KUBATA MACHI/AKITA 010//JAPAN/ (REPRINT); ROYAL PRINCE ALFRED HOSP,PET & NUCL MED DEPT/CAMPERDOWN/NSW/AUSTRALIA/ Journal: JOURNAL OF NUCLEAR CARDIOLOGY, 1998, V5, N3 (MAY-JUN), P313-331 ISSN: 1071-3581 Publication date: 19980500 Publisher: MOSBY-YEAR BOOK INC, 11830 WESTLINE INDUSTRIAL DR, ST LOUIS, MO 63146-3318 Language: English Document Type: REVIEW Abstract: Thallium-201 has been used extensively as a myocardial perfusion agent and to assess myocardial viability. Unlike other Tc-99m-labeled agents such as Tc-99m-sestamibi and Tc-99m-tetro-fosmine, the regional concentration of Tl-201 varies with time, and its kinetics make it a potential candidate for estimating absolute physiologic parameters with kinetic model analysis. This article outlines a strategy for quantitative assessment of regional myocardial blood flow in man using Tl-201 and dynamic single photon emission computed tomography (SPECT), Quantitatively accurate SPECT images that are proportional to the true radioactivity distribution are prerequisites for model-based kinetic analysis. Our technique for quantitative SPECT includes ordered-subset maximum likelihood-expectation maximization (ML-EM) reconstruction with transmission data-based attenuation correction and transmission-dependent convolution subtraction scatter correction. A three-compartment model was found to reproduce the observed regional time-activity curves well, and dog experiments demonstrated that influx rate constant (K-1) values estimated from the dynamic SPECT data correlated well with absolute myocardial blood flow determined by in vitro microspheres for a physiologically wide range of flows. Several possible strategies for simplifying the study procedures, without compromising accuracy, are also presented, which should make absolute quantitation of regional myocardial blood flow feasible using Tl-201 and a conventional SPECT camera in a clinical setting. 1/7/12 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06848535 Genuine Article#: ZW281 Number of References: 7 Title: Whole-body positron emission tomography for oncology imaging using singles transmission scanning with segmentation and ordered subsets expectation maximization (OS-EM) reconstruction Author(s): Bedigian MP (REPRINT) ; Benard F; Smith RJ; Karp JS; Alavi A Corporate Source: UNIV PENN,DEPT RADIOL, DIV NUCL MED, 110 SPRUCE ST/PHILADELPHIA//PA/19104 (REPRINT) Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1998, V25, N6 (JUN), P 659-661 ISSN: 0340-6997 Publication date: 19980600 Publisher: SPRINGER VERLAG, 175 FIFTH AVE, NEW YORK, NY 10010 Language: English Document Type: LETTER 1/7/13 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06825794 Genuine Article#: ZU996 Number of References: 34 Title: Selection of task-dependent diffusion filters for the post-processing of SPECT images Author(s): Beekman FJ (REPRINT) ; Slijpen ETP; Niessen WJ Corporate Source: UNIV UTRECHT HOSP,IMAGE SCI INST, DEPT NUCL MED/UTRECHT//NETHERLANDS/ (REPRINT) Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N6 (JUN), P1713-1730 ISSN: 0031-9155 Publication date: 19980600 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND Language: English Document Type: ARTICLE Abstract: Iterative reconstruction from single photon emission computed tomography (SPECT) data requires regularization to avoid noise amplification and edge artefacts in the reconstructed image. This is often accomplished by stopping the iteration process at a relatively low number of iterations or by post-filtering the reconstructed image. The aim of this paper is to develop a method to automatically select an optimal combination of stopping iteration number and filters for a particular imaging situation. To this end different error measures between the distribution of a phantom and a corresponding filtered SPECT image are minimized for different iteration numbers. As a study example, simulated data representing a brain study are used. For postreconstruction filtering, the performance of 3D linear diffusion (Gaussian filtering) and edge preserving 3D nonlinear diffusion (Catte scheme) is investigated. For reconstruction methods which model the image formation process accurately, error measures between the phantom and the filtered reconstruction are significantly reduced by performing a high number of iterations followed by optimal filtering compared with stopping the iterative process early. Furthermore, this error reduction can be obtained over a wide range of iteration numbers. Only a negligibly small additional reduction of the errors is obtained by including spatial variance in the filter kernel. Compared with Gaussian filtering, Catte diffusion can further reduce the error in some cases. For the examples considered, using accurate image formation models during iterative reconstruction is far more important than the choice of the filter. 1/7/14 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06825792 Genuine Article#: ZU996 Number of References: 23 Title: Application of distance-dependent resolution compensation and post-reconstruction filtering for myocardial SPECT Author(s): Hutton BF (REPRINT) ; Lau YH Corporate Source: WESTMEAD HOSP,DEPT MED PHYS/WESTMEAD/NSW 2145/AUSTRALIA/ (REPRINT); WESTMEAD HOSP,DEPT NUCL MED & ULTRASOUND/WESTMEAD/NSW 2145/AUSTRALIA/ Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N6 (JUN), P1679-1693 ISSN: 0031-9155 Publication date: 19980600 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND Language: English Document Type: ARTICLE Abstract: Compensation for distance-dependent resolution can be directly incorporated in maximum likelihood reconstruction. Our objective was to examine the effectiveness of this compensation using either the standard expectation maximization (EM) algorithm or an accelerated algorithm based on use of ordered subsets (OSEM). We also investigated the application of post-reconstruction filtering in combination with resolution compensation. Using the MCAT phantom, projections were simulated for 360 degrees data, including attenuation and distance-dependent resolution. Projection data were reconstructed using conventional EM and OSEM with subset size 2 and 4, with/without 3D compensation for detector response (CDR). Also post-reconstruction filtering (PRF) was performed using a 3D Butterworth filter of order 5 with various cutoff frequencies (0.2-1.2 cycles cm(-1)). Image quality and reconstruction accuracy were improved when CDR was included. Image noise was lower with CDR for a given iteration number. PRF with cutoff frequency greater than 0.6 cycles cm(-1) improved noise with no reduction in recovery coefficient for myocardium but the effect was less when CDR was incorporated in the reconstruction. CDR alone provided better results than use of PRF without CDR. Results suggest that using CDR without PRF, and stopping at a small number of iterations, may provide sufficiently good results for myocardial SPECT. Similar behaviour was demonstrated for OSEM. 1/7/15 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06814993 Genuine Article#: ZU364 Number of References: 9 Title: Computation of high overrelaxation parameters in iterative image reconstruction Author(s): Schmidlin P (REPRINT) ; Brix G; Bellemann ME; Lorenz WJ Corporate Source: DEUTSCH KREBSFORSCHUNGSZENTRUM,FORSCHUNGSSCHWERPUNKT RADIOL DIAGNOST & THERAPIE/D-69120 HEIDELBERG//GERMANY/ (REPRINT) Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,4 (JUN), P 1737-1742 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Single-projection iterative reconstruction allows the use of high overrelaxation parameters. The parameters can be optimized in a pragmatic way by studying their influence on figures of merit extracted from the image. The resulting parameters are high in the beginning and drop down during further iteration. The value of the overrelaxation parameter which gives the best image after one iteration step is easily found. However, this value will change if an optimum image is postulated after two or more iteration steps. A procedure has been developed which rapidly finds the parameters to be used during a sequence of iteration steps to obtain optimum results for a later approximation. Comparing optimization during one and two steps, the initial parameters obtained with two-step optimization are about twice as high as those with one-step optimization, accelerating convergence by nearly a factor of two. Optimization within three or more steps again leads to different parameter sequences which, however, provide only minor convergence improvement, This indicates that different sequences of parameters may result in similar images, and parameters derived from a typical data set may be widely used for other data. Computation of new parameter sequences by the optimizing procedure is recommended if data from new equipment or with new characteristics have to be processed. 1/7/16 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813313 Genuine Article#: ZU375 Number of References: 21 Title: Comparison of the convergence properties of the It-W and OS-EM algorithms in SPECT Author(s): Wallis JW (REPRINT) ; Miller TR; Dai GM Corporate Source: UNIV WASHINGTON,SCH MED, MALLINCKRODT INST RADIOL, 510 S KINGSHIGHWAY/ST LOUIS//MO/63110 (REPRINT) Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1317-1323 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Rapid convergence of iterative algorithms is a prerequisite for their clinical use in single-photon emission computed-tomography (SPECT). The rate of convergence of two accelerated methods, It-W (JNM 1993;34:1793) and ordered-subset expectation-maximization (OS-EM, IEEE-TMI 1994;13:601) were compared using a resolution phantom containing objects of sizes ranging from 1.0 to 2.5 cm. Object contrast was used as a measure of convergence. Attenuation and depth-dependent blur were modeled in the 90-angle projections and during reconstruction. For both methods, convergence was most rapid at the periphery and slowest in the center, with larger (lower frequency) objects converging most rapidly. When assessed under noise-free conditions, It-W converged faster than both 6- and 15-subset OS-EM. In an ensemble of 25 noisy images both methods gave essentially identical reconstructions when compared at equivalent noise levels using kernel-sieve regularization, but It-W again converged faster than both 6- and 15-subset OS-EM. When assessed using clinical SPECT data, convergence of It-W was faster than 16-subset OS-EM, and similar to 32-subset OS-EM. Thus, the It-W method provides an alternate method of accelerating iterative reconstruction. 1/7/17 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813307 Genuine Article#: ZU375 Number of References: 10 Title: Mean-variance analysis of block-iterative reconstruction algorithms modeling 3D detector response in SPECT Author(s): Lalush DS (REPRINT) ; Tsui BMW Corporate Source: UNIV N CAROLINA,DEPT BIOMED ENGN/CHAPEL HILL//NC/27514 (REPRINT); UNIV N CAROLINA,DEPT RADIOL/CHAPEL HILL//NC/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1280-1287 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: We study the statistical convergence properties of two Cast iterative reconstruction algorithms, the rescaled block-iterative (RBI) and ordered subset (OS) EM algorithms, in the context of cardiac SPECT with 3D detector response modeling. The Monte Carlo method was used to generate nearly noise-free projection data modeling the effects of attenuation, detector response, and scatter from the MCAT phantom. One thousand noise realizations were generated with an average count level approximating a typical Tl-201 cardiac study. Each noise realization was reconstructed using the RBI and OS algorithms for cases with and without detector response modeling. For each iteration up to twenty, we generated mean and variance images, as well as covariance images for six specific locations. Both OS and RBI converged in the mean to results that were close to the noise-free ML-EM result using the same projection model. When detector response was not modeled in the reconstruction, RBI exhibited considerably lower noise variance than OS for the same resolution. When 3D detector response was modeled, the RBI-EM provided a small improvement in the tradeoff between noise level and resolution recovery, primarily in the axial direction, while OS required about half the number of iterations of RBI to reach the same resolution. We conclude that OS is faster than RBI, but may be sensitive to errors in the projection model. Both OS-EM and RBI-EM are effective alternatives to the ML-EM algorithm, but noise level and speed of convergence depend on the projection model used. 1/7/18 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813302 Genuine Article#: ZU375 Number of References: 21 Title: The use of offset cone-beam collimators in a dual head system for combined emission transmission brain SPECT: a feasibility study Author(s): Kamphuis C (REPRINT) ; Beekman FJ Corporate Source: UNIV UTRECHT,IMAGE SCI INST, DEPT NUCL MED/NL-3584 CX UTRECHT//NETHERLANDS/ (REPRINT) Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1250-1254 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Cone-beam (CB) collimators lead to higher sensitivity and resolution in SPECT brain images than parallel beam (PB) collimators. Point sources can be placed in the focal points of the CB collimators in order to obtain additional transmission CT projection data. In the design of a dual-head system with opposing detectors (Opposing Heads System, OHS), it is not possible to position the point sources in the focal points without truncating the patient's head in the projections, even when large crystals are used. Space for the point sources can be created by positioning the cameras at a right angle (Right Angle System, RAS), but such CB systems require collimators with long focal distances or strong offsets for the focal points. It is therefore important to study the effects of focal point positions on the emission image quality. To this end, the following cases were compared in a simulation study: half cone-beams (HCB) in OHS and RAS and quarter cone-beam (QCB) collimators in RAS, each CB with different focal distances (FD). Projections of a disc phantom and a brain phantom acquired with circular orbits were simulated. The size of the crystals was 51 x 38cm. Images were reconstructed iteratively with an Ordered Subset Expectation Maximization algorithm. The disc phantom experiment showed slice-to-slice crosstalk in the CB reconstructions which decreases with increasing focal distance. The CB reconstructions of the brain phantom did not show these artifacts. This study indicates that (i) An OHS with large crystals and HCB collimators provides superior emission image quality compared to RAS with HCB collimators and RAS with QCB collimators. (ii) Dual head systems with large crystals have potential for very high resolution brain imaging. 1/7/19 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813297 Genuine Article#: ZU375 Number of References: 30 Title: A combined half-cone beam and parallel hole collimation system for SPECT brain imaging Author(s): Stone CD (REPRINT) ; Smith MF; Greer KL; Jaszczak RJ Corporate Source: NIH,DEPT NUCL MED, BLDG 10, ROOM 1C401, 10 CTR DR/BETHESDA//MD/20892 (REPRINT); DUKE UNIV,MED CTR, DEPT RADIOL/DURHAM//NC/27710 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1219-1224 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Our research group has recently examined new types of collimator designs with the goal of improving sensitivity and lesion detection for head imaging. One of these collimator designs is a half-cone beam collimator. However, the sensitivity is reduced as objects are removed from the focal line and it does not satisfy Tuy's sufficiency condition. Parallel hole collimation does not have this problem with axial blurring, however, values for sensitivity are not as large as for half-cone collimators. A potential configuration is to use one parallel hole collimator in conjunction with two half-cone beam collimators on a triple camera single photon emission computed tomography (SPECT) system. This might produce results that represent the best of both collimation systems. We acquired projection data with a Defrise disk phantom filled with Tc-99m. A half-cone beam collimator with a focal length of 50 cm was placed on one head of a triple camera SPECT system. A low energy super high resolution (LESR) parallel hole collimator was placed on a second head. Different projection data sets were combined to model acquisition in the three headed gamma camera with three half-cone beam collimators, two half-cone beam and one parallel beam collimators, one half-cone beam and two parallel beam collimators and three parallel beam collimators. Image reconstruction used a modified maximum likelihood maximization-expectation (ML-EM) algorithm. For the reconstruction with three half-cone beam collimators, we observe axial blurring. This is largely reduced with two half-cone beam and one parallel beam collimators. Graphs of the image profiles demonstrate that the blurring along the axial direction is decreased with the addition of parallel hole collimators. 1/7/20 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813296 Genuine Article#: ZU375 Number of References: 19 Title: A comparison of segmentation and emission subtraction for singles transmission in PET. Author(s): Smith RJ (REPRINT) ; Karp JS; Benard F; Alavi A; Gualtieri E; Muehllehner G; Geagan M Corporate Source: UNIV PENN,DEPT RADIOL, 3400 SPRUCE ST/PHILADELPHIA//PA/19104 (REPRINT); UGM MED SYST,/PHILADELPHIA//PA/19104 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1212-1218 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Single photon transmission scans, using Cs-137 (662 keV gamma rays), are performed past-injection for clinical whole body PET studies. Two methods of processing the transmission data are investigated. The first method segments the transmission image into lung and soft tissue volumes. Average attenuation coefficients for 511 keV are applied and this transmission image is forward projected for attenuation correction. In the second method short emission contamination (EC) scans are performed after the singles transmission scans. These are singles transmission scans without a Cs-137 transmission source. These EC scans are then subtracted from the transmission scans to remove contamination of the 662 keV energy window by 511 keV emission gamma rays, From ten patients studied by this method, the EC subtracted transmission images have average soft tissue attenuation coefficients of 0.074/cm, compared to the expected value of 0.086/cm for 662 keV gamma rays. Simple scaling of these transmission images to 511 keV values (0.095/cm) results in quantitative attenuation correction. A comparison of the two methods is made for these ten patient studies. Both methods result in accurate attenuation correction. The segmentation method performs low noise attenuation correction but is more limited to torso studies with the limbs out of the FOV. The EC subtraction method is more versatile and is applicable to the entire body but results in some more noise in the fully corrected images. 1/7/21 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813294 Genuine Article#: ZU375 Number of References: 17 Title: Investigation of approaches to reduce truncation of attenuation maps with simultaneous transmission and emission SPECT imaging Author(s): Narayanan MV (REPRINT) ; King MA; Pan TS; Dahlberg ST Corporate Source: UNIV MASSACHUSETTS,SCH MED, DEPT NUCL MED/WORCESTER//MA/01605 (REPRINT); GE MED SYST,/MILWAUKEE//WI/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1200-1206 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: The limited field of view (FOV) associated with fan beam collimators can lead to truncation of the reconstructed attenuation maps in transmission imaging. We investigated through simulations, five approaches for reducing the truncation of attenuation maps with simultaneous transmission and emission SPECT imaging. These include: 1) the use of longer focal length collimators (65 vs. 104 cm); 2) using a 4 cm lateral table offset to bring the heart closer to the center of the fully sampled region (FSR); 3) using body contouring orbits instead of circular orbits to bring the camera closer to the body; 4) using a larger camera to increase the FSR; and 5) use of an asymmetric fan beam collimator to enlarge the FSR. The three dimensional (3-D) mathematical cardiac torso (MCAT) phantom was used to simulate the activity and attenuation maps. Simulations were carried out for two MCAT configurations with the heart located within. as well as extending beyond, the edge of the I;SR for a 65 cm fan beam collimator. As expected, results indicate that employing a larger camera effectively removes the truncation of attenuation maps seen in normal sized patients. With a standard camera size of 40 cm, the asymmetric fan beam collimator gives results comparable to that obtained using a 104 cm symmetric fan beam collimator. Body contour orbits generally provided better cardiac uniformity at the shorter focal lengths than circular orbits. If any portion of the heart walls extends beyond the FSR for a 65 cm focal length collimator, a judicious combination of using longer focal length collimators along with table offset greatly reduces the amount of truncation in the attenuation maps. improving cardiac uniformity. 1/7/22 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813289 Genuine Article#: ZU375 Number of References: 22 Title: Effects of truncation of transmission projections on cardiac SPECT images acquired by right-angle dual-camera with half-fan-beam collimators Author(s): Beekman FJ (REPRINT) ; Kamphuis C Corporate Source: UNIV UTRECHT HOSP,IMAGE SCI INST, DEPT NUCL MED/NL-3584 CX UTRECHT//NETHERLANDS/ (REPRINT) Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1174-1178 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Right-angle dual-head SPECT systems equipped with half-fan-beam collimators have some advantages compared to right-angle dual-head systems with parallel-hole collimators. A potential drawback of the half-fan-beam system in cardiac studies is that it potentially truncates the transmission data and therefore yields attenuation maps containing inaccuracies in an area to the dorso-lateral region of the torso. The objective of this study is to investigate whether the transmission projection truncation introduces artifacts into iteratively reconstructed emission images of the heart. To this end, a combined cardiac emission transmission study was simulated, modeling 514mm wide detectors and collimators with focal line distances of 890 mm. Emission images were reconstructed iteratively on the basis of truncated and untruncated attenuation maps. The iterative reconstruction methods include the detector response, and compensate for attenuation and scatter in media with non-uniform density. The results indicate that attenuation-and scatter-corrected cardiac studies are not significantly influenced by the truncation of dorso-lateral region of the patient in the transmission projections, even if the patient is extremely large. 1/7/23 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813278 Genuine Article#: ZU375 Number of References: 26 Title: Compensation for distance-dependent resolution in cardiac-perfusion SPECT: Impact on uniformity of wall counts and wall thickness. Author(s): Kohli V (REPRINT) ; King MA; Pan TS; Glick SJ Corporate Source: UNIV MASSACHUSETTS,MED CTR, DEPT NUCL MED/WORCESTER//MA/01605 (REPRINT); UNIV MASSACHUSETTS,DEPT ELECT ENGN/LOWELL//MA/; GE CO,/MILWAUKEE//WI/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1104-1110 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: We investigated the impact on the uniformity of the polar map of the maximum wall count, and on the cardiac wall thickness of several methods used to compensate for distance-dependent resolution (DDR) in cardiac perfusion imaging, Compared were: 1) filtered backprojection (FBP) reconstruction with no correction for attenuation and DDR: 2) FBP with Bellini attenuation compensation (AC); 3) FBP with Bellini AC and frequency distance relationship (FDR) restoration filtering prior to reconstruction: 4) ordered-subset maximum likelihood estimation-maximization (OSEM) reconstruction with just AC, and 5) including DDR compensation and AC in OSEM reconstruction with 3D postreconstruction Gaussian filtering. The best uniformity was obtained with OSEM reconstruction which included just AC. Nearly the same uniformity could he obtained with reconstruction by OSEM which included correction for both AC and DDR when strong 3D post-reconstruction Gaussian filtering was included. With application of this filtering OSEM with compensation for both AC and DDR achieved significantly better recovery; of the original wall thickness at the expense of higher noise magnitude. For the implementations compared herein, it was noted that the modeling of AC and DDR in OSEM yielded a slightly better combination of image quality metrics than FDR restoration. observer detection studies are needed to determine if compensation for DDR and AC does result in improved lesion detection over just compensation for AC. 1/7/24 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813277 Genuine Article#: ZU375 Number of References: 16 Title: Fully 3D Bayesian image reconstruction for the ECAT EXACT HR+ Author(s): Qi JY (REPRINT) ; Leahy RM; Hsu CH; Farquhar TH; Cherry SR Corporate Source: UNIV SO CALIF,INST SIGNAL & IMAGE PROC/LOS ANGELES//CA/90089 (REPRINT); UNIV CALIF LOS ANGELES,SCH MED, CRUMP INST BIOL IMAGING/LOS ANGELES//CA/90024 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1096-1103 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: A fully 3D Bayesian method is described for high resolution reconstruction of images from the Siemens/CTI ECAT EXACT HR+ whole body positron emission tomography (PET) scanner. To maximize resolution recovery from the system we model depth dependent geometric efficiency, intrinsic detector efficiency, photon pair non-colinearity, crystal penetration and inter-crystal scatter. We also explicitly model the effects of axial rebinning and angular mashing on the detection probability or system matrix. By fully exploiting sinogram symmetries and using a factored system matrix and automated indexing schemes, we are able to achieve substantial savings in both the storage size and time required to compute forward and backward projections. Reconstruction times are further reduced using multi-threaded programming on a four processor Unix server. Bayesian reconstructions are computed using a Huber prior and a shifted-Poisson likelihood model that accounts for the effects of randoms subtraction and scatter. Reconstructions of phantom data show that the 3D Bayesian method can achieve improved FWHM resolution and contrast recovery ratios at matched background noise levels compared to both the 3D reprojection method and an OSEM method based on the shifted-Poisson model. 1/7/25 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06813275 Genuine Article#: ZU375 Number of References: 15 Title: Fast reconstruction of 3D PET data with accurate statistical modeling Author(s): Comtat C (REPRINT) ; Kinahan PE; Defrise M; Michel C; Townsend DW Corporate Source: UNIV PITTSBURGH,DEPT RADIOL/PITTSBURGH//PA/15260 (REPRINT); FREE UNIV BRUSSELS,AZ VUB, DIV NUCL MED/BRUSSELS//BELGIUM/; CATHOLIC UNIV LOUVAIN,PET LAB/B-3000 LOUVAIN//BELGIUM/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1998, V45, N3,2 (JUN), P 1083-1089 ISSN: 0018-9499 Publication date: 19980600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: This paper presents the results of combining high sensitivity 3D PET whole-body acquisition followed by fast 2D iterative reconstruction methods based on accurate statistical models. This combination is made possible by Fourier rebinning (FORE), which accurately converts a 3D data set to a set of 2D sinograms. The combination of volume imaging with statistical reconstruction allows improvement of noise-bias trade-offs when image quality is dominated by measurement statistics. The rebinning of the acquired data into a 2D data set reduces the computation time of the reconstruction. For both penalized weighted least-squares (PWLS) and ordered-subset EM: (OSEM) reconstruction methods, the usefulness of a realistic model of the expected measurement statistics is shown when the data are pre-corrected for attenuation and random and scattered coincidences, as required for the FORE rebinning algorithm. The results presented are based on 3D simulations of whole-body scans that include the major statistical effects of PET acquisition and data correction procedures. As the PWLS method requires knowledge of the variance of the projection data, a simple model for the effect of FORE rebinning on data variance is developed. 1/7/26 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06760772 Genuine Article#: ZQ134 Number of References: 24 Title: Evaluation of a cross-validation stopping rule in MLE SPECT reconstruction Author(s): Falcon C; Juvells I; Pavia J; Ros D (REPRINT) Corporate Source: UNIV BARCELONA,FAC MED, LAB BIOFIS & BIOENGN, CASANOVA 143/BARCELONA 08036//SPAIN/ (REPRINT); UNIV BARCELONA,FAC MED, LAB BIOFIS & BIOENGN/BARCELONA 08036//SPAIN/; UNIV BARCELONA,DEPT FIS APLICADA & ELECT, LAB OPT/E-08028 BARCELONA//SPAIN/; HOSP CLIN BARCELONA,SERV MED NUCL/BARCELONA//SPAIN/ Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N5 (MAY), P1271-1283 ISSN: 0031-9155 Publication date: 19980500 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND Language: English Document Type: ARTICLE Abstract: One of the problems in the routine use of the maximum-likelihood estimator method-expectation maximization (MLE-EM) algorithm is to decide when the iterative process should be stopped. We studied a cross-validation stopping rule to assess its usefulness in SPECT. We tested this stopping rule criterion in the MLE-EM algorithm without acceleration as well as in two accelerating algorithms, the successive substitutions algorithm (SSA) and the additive algorithm (AA). Different values of an acceleration factor were tested in SSA and AA. Our results from numerical and physical phantoms show that the stopping rule based on the cross-validation ratio (CVR) takes into account the similarity of the reconstructed image to the ideal image, noise and the contrast of the image. CVR yields reconstructed images with balanced values of the figures of merit (FOM) employed to assess the image quality. The CVR criterion can be used in the original MLE-EM algorithm as well as in SSA and AA. The reconstructed images obtained with SSA and AA showed FOM values that were very similar. These results were justified by considering AA to be an approximate form of SSA. The range of validity for the acceleration factor in SSA and AA was found to be [1,2]. In this range, an inverse function connects the acceleration factor to the number of iterations needed to attain prefixed values of FOMs. 1/7/27 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06725677 Genuine Article#: ZN487 Number of References: 41 Title: Image restoration and reconstruction with a Bayesian approach Author(s): Kao CM (REPRINT) ; Pan XC; Chen CT; Wong WH Corporate Source: UNIV CHICAGO,DEPT RADIOL, 5841 S MARYLAND AVE/CHICAGO//IL/60637 (REPRINT); UCLA,STAT PROGRAM/LOS ANGELES//CA/90095 Journal: MEDICAL PHYSICS, 1998, V25, N5 (MAY), P600-613 ISSN: 0094-2405 Publication date: 19980500 Publisher: AMER INST PHYSICS, CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 Language: English Document Type: ARTICLE Abstract: We have extended Johnson's Bayesian method for image restoration and reconstruction by introducing diagonal line sites, using symmetric neighborhood configurations, and employing an additional hyperparameter for estimation of line sites. A general formulation for arbitrary neighborhood configurations was derived. The major part of this paper deals with the conduct of computer simulations intended to examine the effect of the hyperparameters, the diagonal line sites, and the size of the neighborhood configuration on the performance of the proposed Bayesian method. We show that, for optimal performance, distinct hyperparameters should be used for the intensity sites and line sites. The results also suggest that a large neighborhood configuration should be used. By comparing the near-optimal restored images, we demonstrated that the use of diagonal line sites, along with the symmetric configurations thus made possible, can effectively remove the blocky edge artifacts and produce images of better quality. When the method was applied to positron emission tomography (PET) image reconstruction, our results showed that the quality of the reconstructed images was improved for both computer-simulated and real patient PET data. (C) 1998 American Association of Physicists in Medicine. 1/7/28 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06723949 Genuine Article#: ZN446 Number of References: 32 Title: Projection space image reconstruction using strip functions to calculate pixels more ''Natural'' for modeling the geometric response of the SPECT collimator Author(s): Hsieh YL; Zeng GSL; Gullberg GT (REPRINT) Corporate Source: UNIV UTAH,MED IMAGING RES LAB, DEPT RADIOL, CAMT, 729 ARAPEEN DR/SALT LAKE CITY//UT/84108 (REPRINT); UNIV UTAH,MED IMAGING RES LAB, DEPT RADIOL, CAMT/SALT LAKE CITY//UT/84108 Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1998, V17, N1 (FEB), P24-44 ISSN: 0278-0062 Publication date: 19980200 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: The spatially varying geometric response of the collimator-detector system in single photon emission computed tomography (SPECT) causes loss in resolution, shape distortions, reconstructed density nonuniformity, and quantitative inaccuracies. A projection space image reconstruction algorithm is used to correct these reconstruction artifacts. The projectors F use strip functions to calculate pixels more ''natural'' far modeling the two-dimensional (2-D) geometric response of the SPECT collimator transaxially to the axis of rotation. These projectors are defined by summing the intersection of an array of multiple strips rotated at equal angles to approximate the ideal system geometric response of the collimator. Two projection models were evaluated for modeling the system geometric response function. For one projector each strip is of equal weight, for the other projector a Gaussian weighting is used, Parallel beam and fan beam projections of a physical three-dimensional (3-D) Hoffman brain phantom and a Jaszczak cold rod phantom were used to evaluate the geometric response correction Reconstructions were obtained by using the singular value decomposition (SVD) method and the iterative conjugate gradient algorithm to solve for q in the imaging equation FGq = p, where p is the projection measurement. The projector F included the new models for the geometric response, whereas, the backprojector G did not always model the geometric response in order to increase the computational speed. The final reconstruction was obtained by sampling the backprojection Gq at a discrete array of points. Reconstructions produced by the two proposed projectors showed improved resolution when compared against a unit-strip ''natural'' pixel model, the conventional image pixelized model with ray tracing to calculate the geometric response, and the filtered backprojection algorithm, When the reconstruction is displayed on fine grid points, the continuity and resolution of the image is preserved without the ring artifacts seen in the unit-strip ''natural'' pixel model. With present computing power, the geometric response correction using the proposed projection space reconstruction approach is not get feasible for routine clinical use. 1/7/29 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06717804 Genuine Article#: ZM931 Number of References: 17 Title: Visualization of the cervical spinal cord with FDG and high-resolution PET Author(s): Kamoto Y (REPRINT) ; Sadato N; Yonekura Y; Tsuchida T; Uematsu H ; Waki A; Uchida K; Baba H; Imura S; Konishi J Corporate Source: KYOTO UNIV,FAC MED, DEPT NUCL MED, SAKYO KU, 54 SHOGOINKAWAHARA CHO/KYOTO 60601//JAPAN/ (REPRINT); FUKUI MED SCH,DEPT ORTHOPAED SURG/FUKUI 91011//JAPAN/; FUKUI MED SCH,BIOMED IMAGING RES CTR/FUKUI 91011//JAPAN/ Journal: JOURNAL OF COMPUTER ASSISTED TOMOGRAPHY, 1998, V22, N3 (MAY-JUN) , P487-491 ISSN: 0363-8715 Publication date: 19980500 Publisher: LIPPINCOTT-RAVEN PUBL, 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 Language: English Document Type: ARTICLE Abstract: Purpose: Our aim was to evaluate the visibility of the cervical spinal cord with [F-18]2-fluoro-2-deoxyglucose (FDG) and a high-resolution PET scanner and to quantify the glucose utilization by the cervical cord. Method: Twenty-one normal subjects and three cervical myelopathy patients were studied. The visibility of the cervical spinal cord in sagittal and coronal sections was evaluated. The metabolic rate of glucose (MRGlu) and standardized uptake value (SUV) of FDG in the cord were calculated. Results: The entire cervical spinal cord was clearly visualized in 57% of the subjects: the upper cord in 81%, the middle cord in 73%, and the lower cord in 57%. The MRGlu of the normal cord was 1.93 +/- 0.37 mg/100 g/min. SUV was constant across all the vertebral levels and negatively correlated with subject age. In the myelopathy patients, the SUV of the entire cervical cord was lower than in the age-matched normal subjects. Conclusion: These preliminary results indicate that the cervical spinal cord can be visualized as a normal structure in routine head and neck PET imaging and that FDG-PET may provide quantitative information about spinal cord disorders. 1/7/30 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06658294 Genuine Article#: ZH948 Number of References: 9 Title: Median root prior and ordered subsets in Bayesian image reconstruction of single-photon emission tomography Author(s): Seret A (REPRINT) Corporate Source: FREE UNIV BRUSSELS,HOP ERASME, SERV RADIOISOTOPES, 808 ROUTE LENNIK/B-1070 BRUSSELS//BELGIUM/ (REPRINT) Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1998, V25, N3 (MAR), P 215-219 ISSN: 0340-6997 Publication date: 19980300 Publisher: SPRINGER VERLAG, 175 FIFTH AVE, NEW YORK, NY 10010 Language: English Document Type: ARTICLE Abstract: Median root prior allows Bayesian image reconstruction without any a priori knowledge of the final solution. It limits the noise generated by maximum likelihood-expectation maximization, including when the ordered subsets accelerating procedure is used. Therefore the number of iterations can be optimized to obtain the best resolution for cold lesions. Moreover, the higher the number of subsets, the better the contrast, with optimal results for subsets containing between four and eight projections. 1/7/31 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06643795 Genuine Article#: ZH069 Number of References: 25 Title: Comparison of frequency-distance relationship and Gaussian-diffusion-based methods of compensation for distance-dependent spatial resolution in SPECT imaging Author(s): Kohli V; King MA (REPRINT) ; Glick SJ; Pan TS Corporate Source: UNIV MASSACHUSETTS,MED CTR, DEPT NUCL MED, 55 LAKE AVE N/WORCESTER//MA/01655 (REPRINT); UNIV MASSACHUSETTS,MED CTR, DEPT NUCL MED/WORCESTER//MA/01655; UNIV LOWELL,DEPT ELECT ENGN/LOWELL//MA/01854; GE CO,APPL SCI LAB/MILWAUKEE//WI/53201 Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N4 (APR), P1025-1037 ISSN: 0031-9155 Publication date: 19980400 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: The goal of this investigation was to compare resolution recovery versus noise level of two methods for compensation of distance-dependent resolution (DDR) in SPECT imaging. The two methods of compensation were restoration filtering based on the frequency-distance relationship (FDR) prior to iterative reconstruction, and modelling DDR in the projector/backprojector pair employed in iterative reconstruction. FDR restoration filtering was computationally faster than modelling the detector response in iterative reconstruction. Using Gaussian diffusion to model the detector response in iterative reconstruction sped up the process by a factor of 2.5 over frequency domain filtering in the projector/backprojector pair. Gaussian diffusion modelling resulted in a better resolution versus noise tradeoff than either FDR restoration filtering or solely modelling attenuation in the projector/backprojector pair of iterative reconstruction. For the pixel size investigated herein (0.317 cm), accounting for DDR in the projector/backprojector pair by Gaussian diffusion, or by applying a blurring function based on the distance from the face of the collimator at each distance, resulted in very similar resolution recovery and slice noise level. 1/7/32 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06643793 Genuine Article#: ZH069 Number of References: 21 Title: High-resolution 3D Bayesian image reconstruction using the microPET small-animal scanner Author(s): Qi JY; Leahy RM (REPRINT) ; Cherry SR; Chatziioannou A; Farquhar TH Corporate Source: UNIV SO CALIF,INST SIGNAL & IMAGE PROC, 3740 MCCLINTOCK AVE, EEB400/LOS ANGELES//CA/90089 (REPRINT); UNIV SO CALIF,INST SIGNAL & IMAGE PROC/LOS ANGELES//CA/90089; UNIV CALIF LOS ANGELES,SCH MED, CRUMP INST BIOL IMAGING, DIV IMAGING SCI/LOS ANGELES//CA/90024 Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N4 (APR), P1001-1013 ISSN: 0031-9155 Publication date: 19980400 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: A Bayesian method is described for reconstruction of high-resolution 3D images from the microPET small-animal scanner. Resolution recovery is achieved by explicitly modelling the depth dependent geometric sensitivity for each voxel in combination with an accurate detector response model that includes factors due to photon pair non-collinearity and inter-crystal scatter and penetration. To reduce storage and computational costs we use a factored matrix in which the detector response is modelled using a sinogram blurring kernel. Maximum a posteriori (MAP) images are reconstructed using this model in combination with a Poisson likelihood function and a Gibbs prior on the image. Reconstructions obtained from point source data using the accurate system model demonstrate a potential for near-isotropic FWHM resolution of approximately 1.2 mm at the center of the held of view compared with approximately 2 mm when using an analytic 3D reprojection (3DRP) method with a ramp filter. These results also show the ability of the accurate system model to compensate for resolution loss due to crystal penetration producing nearly constant radial FWHM resolution of 1 mm out to a 4 mm radius. Studies with a point source in a uniform cylinder indicate that as the resolution of the image is reduced to control noise propagation the resolution obtained using the accurate system model is superior to that obtained using 3DRP at matched background noise levels. Additional studies using pie phantoms with hot and cold cylinders of diameter 1-2.5 mm and (18)FDG animal studies appear to confirm this observation. 1/7/33 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06643784 Genuine Article#: ZH069 Number of References: 45 Title: Quantitative cardiac SPECT in three dimensions: validation by experimental phantom studies Author(s): Liang Z (REPRINT) ; Ye J; Cheng J; Li J; Harrington D Corporate Source: SUNY STONY BROOK,DEPT RADIOL, 4TH FLOOR, ROOM 092-HSC/STONY BROOK//NY/11794 (REPRINT); SUNY STONY BROOK,DEPT COMP SCI & ELECT ENGN/STONY BROOK//NY/11794 Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N4 (APR), P905-920 ISSN: 0031-9155 Publication date: 19980400 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: A mathematical framework for quantitative SPECT (single photon emission computed tomography) reconstruction of the heart is presented. An efficient simultaneous compensation approach to the reconstruction task is described. The implementation of the approach on a digital computer is delineated. The approach was validated by experimental data acquired from chest phantoms. The phantoms consisted of a cylindrical elliptical tank of Plexiglass, a cardiac insert made of Plexiglass, a spine insert of packed bone meal and lung inserts made of styrofoam beads alone. Water bags were added to simulate different body characteristics. Comparison between the quantitative reconstruction and the conventional FBP (filtered backprojection) method was performed. The FBP reconstruction had a poor quantitative accuracy and varied for different body configurations. Significant improvement in reconstruction accuracy by the quantitative approach was demonstrated with a moderate computing time on a currently available desktop computer. Furthermore, the quantitative reconstruction was robust for different body characteristics. Therefore, the quantitative approach has the potential for clinical use. 1/7/34 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06643781 Genuine Article#: ZH069 Number of References: 23 Title: Block-iterative techniques for fast 4D reconstruction using a priori motion models in gated cardiac SPECT Author(s): Lalush DS (REPRINT) ; Tsui BMW Corporate Source: UNIV N CAROLINA,DEPT BIOMED ENGN/CHAPEL HILL//NC/27599 (REPRINT); UNIV N CAROLINA,DEPT RADIOL/CHAPEL HILL//NC/27599 Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N4 (APR), P875-886 ISSN: 0031-9155 Publication date: 19980400 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: We introduce a fast block-iterative maximum a posteriori (MAP) reconstruction algorithm and apply it to four-dimensional reconstruction of gated SPECT perfusion studies. The new algorithm, called RBI-MAP, is based on the rescaled block iterative EM (RBI-EM) algorithm. We develop RBI-MAP based on similarities between the RBI-EM, ML-EM and MAP-EM algorithms. RBI-MAP requires far fewer iterations than MAP-EM, and so should result in acceleration similar to that obtained from using RBI-EM or OS-FM as opposed to ML-EM. When complex four-dimensional clique structures are used in the prior, however, evaluation of the smoothing prior dominates the processing time. We show that a simple scheme for updating the prior term in the heart region only for RBI-MAP results in savings in processing time of a factor of six over MAP-EM. The RBI-MAP algorithm incorporating 3D collimator-detector response compensation is demonstrated on a simulated Tc-99m gated perfusion study. Results of RBI-MAP are compared with RBI-EM followed by a 4D linear filter. For the simulated study, we find that RBI-MAP provides consistently higher defect contrast for a given degree of noise smoothing than does filtered RBI-EM. This is an indication that RBI-MAP smoothing does less to degrade resolution gained from 3D detector response compensation than does a linear filter. We conclude that RBI-MAP can provide smooth four-dimensional reconstructions with good visualization of heart structures in clinically realistic processing times. 1/7/35 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06643780 Genuine Article#: ZH069 Number of References: 24 Title: Fast implementations of reconstruction-based scatter compensation in fully 3D SPECT image reconstruction Author(s): Kadrmas DJ (REPRINT) ; Frey EC; Karimi SS; Tsui BMW Corporate Source: UNIV N CAROLINA,DEPT BIOMED ENGN, CAMPUS BOX 7575, 152 MACNIDER HALL/CHAPEL HILL//NC/27599 (REPRINT); UNIV N CAROLINA,DEPT RADIOL/CHAPEL HILL//NC/27599 Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N4 (APR), P857-873 ISSN: 0031-9155 Publication date: 19980400 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: Accurate scatter compensation in SPECT can be performed by modelling the scatter response function during the reconstruction process. This method is called reconstruction-based scatter compensation (RBSC). It has been shown that RBSC has a number of advantages over other methods of compensating for scatter, but using RBSC for fully 3D compensation has resulted in prohibitively long reconstruction times. In this work we propose two new methods that can be used in conjunction with existing methods to achieve marked reductions in RBSC reconstruction times. The first method, coarse-grid scatter modelling, significantly accelerates the scatter model by exploiting the fact that scatter is dominated by low-frequency information. The second method, intermittent RBSC, further accelerates the reconstruction process by limiting the number of iterations during which scatter is modelled. The fast implementations were evaluated using a Monte Carlo simulated experiment of the 3D MCAT phantom with Te-99m tracer, and also using experimentally acquired data with Tl-201 tracer. Results indicated that these fast methods can reconstruct, with fully 3D compensation, images very similar to those obtained using standard RBSC methods, and in reconstruction times that are an order of magnitude shorter. Using these methods, fully 3D iterative reconstruction with RBSC can be performed well within the realm of clinically realistic times (under 10 minutes for 64 x 64 x 24 image reconstruction). 1/7/36 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06643778 Genuine Article#: ZH069 Number of References: 9 Title: Fast accurate iterative reconstruction for low-statistics positron volume imaging Author(s): Reader AJ (REPRINT) ; Erlandsson K; Flower MA; Ott RJ Corporate Source: ROYAL MARSDEN NHS TRUST,JOINT DEPT PHYS, CANC RES INST, DOWNS RD/SUTTON SM2 5PT/SURREY/ENGLAND/ (REPRINT) Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N4 (APR), P835-846 ISSN: 0031-9155 Publication date: 19980400 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: A fast accurate iterative reconstruction (FAIR) method suitable for low-statistics positron volume imaging has been developed. The method, based on the expectation maximization-maximum likelihood (EM-ML) technique, operates on list-mode data rather than histogrammed projection data and can, in just one pass through the data, generate images with the same characteristics as several ML iterations. Use of list-mode data preserves maximum sampling accuracy and implicitly ignores lines of response (LORs) in which no counts were recorded. The method is particularly suited to systems where sampling accuracy can be lost by histogramming events into coarse LOR bins, and also to sparse data situations such as fast whole-body and dynamic imaging where sampling accuracy may be compromised by storage requirements and where reconstruction time can be wasted by including LORs with no counts. The technique can be accelerated by operating on subsets of list-mode data which also allows scope for simultaneous data acquisition and iterative reconstruction. The method is compared with a standard implementation of the EM-ML technique and is shown to offer improved resolution, contrast and noise properties as a direct result of using improved spatial sampling, limited only by hardware specifications. 1/7/37 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06643777 Genuine Article#: ZH069 Number of References: 21 Title: Intercomparison of four reconstruction techniques for positron volume imaging with rotating planar detectors Author(s): Reader AJ (REPRINT) ; Visvikis D; Erlandsson K; Ott RJ; Flower MA Corporate Source: ROYAL MARSDEN NHS TRUST,JOINT DEPT PHYS, CANC RES INST, DOWNS RD/SUTTON SM2 5PT/SURREY/ENGLAND/ (REPRINT) Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N4 (APR), P823-834 ISSN: 0031-9155 Publication date: 19980400 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: Four reconstruction techniques for positron volume imaging have been evaluated for scanners based on rotating planar detectors using measured and simulated data. The four techniques compared are backproject then filter (BPF), the 3D reprojection (3D RP) method for 3D filtered backprojection (FBP), Fourier rebinning (FORE) in conjunction with 2D FBP (FORE + 2D FBP) and 3D ordered subsets expectation maximization (3D OSEM). The comparison was based on image resolution and on the trade-off between contrast and noise. In general FORE + 2D FBP offered a better contrast-noise trade-off than 3D RP, whilst 3D RP offered a better trade-off than BPF. Unlike 3D RP, FORE + 2D FBP did not suffer any contrast degradation effect at the edges of the axial field of view, but was unable to take as much advantage from high-accuracy data as the other methods. 3D OSEM gave the best contrast at the expense of greater image noise. BPF, which demonstrated generally inferior contrast-noise behaviour due to use of only a subset of the data, gave more consistent spatial resolution over the field of view than the projection-data based methods, and was best at taking full advantage of high-accuracy data. 1/7/38 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06643769 Genuine Article#: ZH069 Number of References: 16 Title: Iterative reconstruction for helical CT: a simulation study Author(s): Nuyts J (REPRINT) ; DeMan B; Dupont P; Defrise M; Suetens P; Mortelmans L Corporate Source: KATHOLIEKE UNIV LEUVEN,DEPT NUCL MED/B-3001 LOUVAIN//BELGIUM/ (REPRINT); KATHOLIEKE UNIV LEUVEN,ESAT MI2/B-3001 LOUVAIN//BELGIUM/; FREE UNIV BRUSSELS,/BRUSSELS//BELGIUM/ Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N4 (APR), P729-737 ISSN: 0031-9155 Publication date: 19980400 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: Iterative reconstruction algorithms for helical CT are presented. The algorithms are derived from two-dimensional reconstruction algorithms, by adapting the projector/backprojector to the helical orbit of the source, and by constraining the axial frequencies with a Gaussian sieve. Simulations have been carried out and the performance of the iterative algorithms is compared to that of filtered backprojection of synthetic (interpolated) two-dimensional sinograms. The iterative algorithms produce superior bias-noise curves. Axial resolution is superior, but disturbing edge-artefacts are introduced. 1/7/39 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06572908 Genuine Article#: ZB735 Number of References: 39 Title: Parametric image reconstruction using spectral analysis of PET projection data Author(s): Meikle SR (REPRINT) ; Matthews JC; Cunningham VJ; Bailey DL; Livieratos L; Jones T; Price P Corporate Source: ROYAL PRINCE ALFRED HOSP,DEPT PET & NUCL MED, MISSENDEN RD/CAMPERDOWN/NSW 2050/AUSTRALIA/ (REPRINT); HAMMERSMITH HOSP,ROYAL POSTGRAD MED SCH, MRC, CYCLOTRON UNIT/LONDON W12 0NN//ENGLAND/ Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N3 (MAR), P651-666 ISSN: 0031-9155 Publication date: 19980300 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: Spectral analysis is a general modelling approach that enables calculation of parametric images from reconstructed tracer kinetic data independent of an assumed compartmental structure. We investigated the validity of applying spectral analysis directly to projection data motivated by the advantages that: (i) the number of reconstructions is reduced by an order of magnitude and (ii) iterative reconstruction becomes practical which may improve signal-to-noise ratio (SNR). A dynamic software phantom with typical 2[C-11]thymidine kinetics was used to compare projection-based and image-based methods and to assess bias-variance trade-offs using iterative expectation maximization (EM) reconstruction. We found that the two approaches are not exactly equivalent due to properties of the non-negative least-squares algorithm. However, the differences are small (<5%) and mainly affect parameters related to early and late time points on the impulse response function (K-1 and, to a lesser extent, VD). The optimal number of EM iterations was 15-30 with up to a two-fold improvement in SNR over filtered back projection. We conclude that projection-based spectral analysis with EM reconstruction yields accurate parametric images with high SNR and has potential application to a wide range of positron emission tomography ligands. 1/7/40 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06564271 Genuine Article#: ZB313 Number of References: 40 Title: Implementation of a model-based nonuniform scatter correction scheme for SPECT Author(s): Welch A (REPRINT) ; Gullberg GT Corporate Source: ABERDEEN PET UNIT,DEPT BIOMED PHYS & BIOENGN/ABERDEEN AB25 2ZD//SCOTLAND/ (REPRINT); UNIV UTAH,DEPT RADIOL, MED IMAGING RES LAB/SALT LAKE CITY//UT/84112 Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1997, V16, N6 (DEC), P 717-726 ISSN: 0278-0062 Publication date: 19971200 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: In this paper four scatter-compensation schemes are considered, The four schemes are all based on a previously developed two-dimensional (2-D) scatter model, Reconstruction is achieved using the iterative expectation-maximization maximum-likelihood (EM-ML) algorithm. The schemes consist of: 1) including the model in both the forward and hack projector; 2) just including the model in the forward projector; 3) and 4) implementing the model in a subtraction and addition scheme, respectively, Monte Carlo simulated projection data are used to test the accuracy, convergence properties, and noise properties of the four scatter-compensation schemes. Data are simulated for both uniformly and nonuniformly attenuating objects, The results show that all four correction schemes yield images which are similar in terms of accuracy to that obtained from reconstructing scatter-free data, The subtraction scheme is shown to converge faster than the other compensation schemes, both in terms of iterations and actual time required for reconstruction, The scheme in which the model is only used in the forward-projector and the scatter-addition scheme both performs slightly better, in terms of signal-to-noise ratio (SNR), than the subtraction scheme, However, the forward projector scheme requires significantly more CPU time for reconstruction. The correction scheme in which the scatter model was included in both the forward and backprojectors is shown to produce accurate images with SNR's higher than even a perfect scatter rejection scheme, dWhile the scatter correction scheme with the model in both the forward projector and backprojector has superior noise properties to the other algorithms, the results suggest that the faster subtraction/addition schemes will probably prove most useful for routine clinical scatter compensation. 1/7/41 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06491071 Genuine Article#: YW974 Number of References: 41 Title: Reducing the influence of the partial volume effect on SPECT activity quantitation with 3D modelling of spatial resolution in iterative reconstruction Author(s): Pretorius PH; King MA (REPRINT) ; Pan TS; deVries DJ; Glick SJ; Byrne CL Corporate Source: UNIV MASSACHUSETTS,MED CTR, 55 LAKE AVE N/WORCESTER//MA/01655 (REPRINT); UNIV MASSACHUSETTS,MED CTR/WORCESTER//MA/01655; UNIV ORANGE FREE STATE,/ZA-9300 BLOEMFONTEIN//SOUTH AFRICA/; UNIV MASSACHUSETTS,/LOWELL//MA/ Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1998, V43, N2 (FEB), P407-420 ISSN: 0031-9155 Publication date: 19980200 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: Quantitative parameters such as the maximum and total counts in a volume are influenced by the partial volume effect. The magnitude of this effect varies with the non-stationary and anisotropic spatial resolution in SPECT slices. The objective of this investigation was to determine whether iterative reconstruction which includes modelling of the three-dimensional (3D) spatial resolution of SPECT imaging can reduce the impact of the partial volume effect on the quantitation of activity compared with filtered backprojection (FBP) techniques which include low-pass, and linear restoration filtering using the frequency distance relationship (FDR). The iterative reconstruction algorithms investigated were maximum-likelihood expectation-maximization (MLEM), MLEM with ordered subset acceleration (MLOS), and MLEM with acceleration by the rescaled-block-iterative technique (ML-RBI). The SIMIND Monte Carlo code was used to simulate small hot spherical objects in an elliptical cylinder with and without uniform background activity as imaged by a low-energy ultra-high-resolution (LEUHR) collimator. Centre count ratios (CCRs) and total count ratios (TCRs) were determined as the observed counts over true counts. CCRs were unstable while TCRs had a bias of similar to 10% for all iterative techniques. The variance in the TCRs for ML-OS and ML-RBI was clearly elevated over that of MLEM, with ML-RBI having the smaller elevation. TCRs obtained with FDR-Wiener filtering had a larger bias (similar to 30%) than any of the iterative reconstruction methods but near stationarity is also reached. Butterworth filtered results varied by 9.7% from the centre to the edge. The addition of background has an influence on the convergence rate and noise properties of iterative techniques. 1/7/42 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06463705 Genuine Article#: YV178 Number of References: 9 Title: World Wide Web interface for advanced SPECT reconstruction algorithms implemented on a remote massively parallel computer Author(s): Formiconi AR (REPRINT) ; Passeri A; Guelfi MR; Masoni M; Pupi A; Meldolesi U; Malfetti P; Calori L; Guidazzoli A Corporate Source: UNIV FLORENCE,DEPT CLIN PHYSIOPATHOL/FLORENCE//ITALY/ (REPRINT); CINECA,/BOLOGNA//ITALY/ Journal: INTERNATIONAL JOURNAL OF MEDICAL INFORMATICS, 1997, V47, N1-2 (NOV ), P125-138 ISSN: 1386-5056 Publication date: 19971100 Publisher: ELSEVIER SCI IRELAND LTD, CUSTOMER RELATIONS MANAGER, BAY 15, SHANNON INDUSTRIAL ESTATE CO, CLARE, IRELAND Language: English Document Type: ARTICLE Abstract: Data from Single Photon Emission Computed Tomography (SPECT) studies are blurred by inevitable physical phenomena occurring during data acquisition. These errors may be compensated by means of reconstruction algorithms which take into account accurate physical models of the data acquisition procedure. Unfortunately, this approach involves high memory requirements as well as a high computational burden which cannot be afforded by the computer systems of SPECT acquisition devices. In this work the possibility of accessing High Performance Computing and Networking (HPCN) resources through a World Wide Web interface for the advanced reconstruction of SPECT data in a clinical environment was investigated. An iterative algorithm with an accurate model of the variable system response was ported on the Multiple Instruction Multiple Data (MIMD) parallel architecture of a Cray T3D massively parallel computer. The system was accessible even from low cost PC-based workstations through standard TCP/IP networking. A speedup Factor of 148 was predicted by the benchmarks run on the Gray T3D. A complete brain study of 30 (64 x 64) slices was reconstructed from a set of 90 (64 x 64) projections with ten iterations of the conjugate gradients algorithm in 9 s which corresponds to an actual speed-up factor of 135. The technique was extended to a more accurate 3D modeling of the system response for a true 3D reconstruction of SPECT data, the reconstruction time of the same data set with this more accurate model was 5 min. This work demonstrates the possibility of exploiting remote HPCN resources from hospital sites by means of low cost workstations using standard communication protocols and an user-friendly WWW interface without particular problems for routine use. (C) 1997 Elsevier Science B.V. 1/7/43 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06430787 Genuine Article#: YR214 Number of References: 27 Title: Effects of scatter and attenuation correction on quantitative assessment of regional cerebral blood flow with SPECT Author(s): Iida H (REPRINT) ; Narita Y; Kado H; Kashikura A; Sugawara S; Shoji Y; Kinoshita T; Ogawa T; Eberl S Corporate Source: RES INST BRAIN & BLOOD VESSELS,DEPT RADIOL & NUCL MED, 6-10 SHENSHU KUBOTA MACHI/AKITA//JAPAN/ (REPRINT); RES INST BRAIN & BLOOD VESSELS,DEPT RADIOL/AKITA//JAPAN/; RES INST BRAIN & BLOOD VESSELS,DEPT NUCL MED/AKITA//JAPAN/; ROYAL PRINCE ALFRED HOSP,/SYDNEY/NSW/AUSTRALIA/ Journal: JOURNAL OF NUCLEAR MEDICINE, 1998, V39, N1 (JAN), P181-189 ISSN: 0161-5505 Publication date: 19980100 Publisher: SOC NUCLEAR MEDICINE INC, 1850 SAMUEL MORSE DR, RESTON, VA 20190-5316 Language: English Document Type: ARTICLE Abstract: Appropriate corrections for scatter and attenuation correction are prerequisites for quantitative SPECT studies. However, in most cerebral SPECT studies, uniform attenuation in the head is assumed, and scatter is usually neglected. This study evaluated the effect of attenuation correction and scatter correction on quantitative values and image contrast. Methods: Studies were performed in six normal volunteers (ages 22-26 yr) following intravenous I-123-IMP administration using a rotating, dual-head gamma camera. A transmission scan was acquired with a Tc-99m rod source (74 MBq) placed at the focus of a symmetrical fanbeam collimator. Data were reconstructed using two attenuation coefficient (mu) maps: quantitative mu map from the transmission scan and a uniform mu map generated by edge detection of the reconstructed images. Narrow and broad beam mu values were used with and without scatter correction, respectively. Scatter was corrected with transmission-dependent convolution subtraction and triple-energy window techniques. Quantitative rCBF images were calculated by the previously validated IMP-autoradiograph technique, and they were compared with those obtained by O-15-water and PET. SPECT and PET images were registered to MRI studies, and rCBF values were compared in 39 ROIs selected on MRI. Results: Clear differences were observed in rCBF images between the measured and constant mu maps in the lower slices due to the airways and in the higher slices due to increased skull attenuation. However, differences were < 5% in all cerebral tissue regions, thus assumption of uniform mu introduces little bias. The scatter correction was found to increase the image contrast significantly i.e., rCBF increased by 20%-30% in gray matter and decreased in white matter regions by 10%-20% after scatter correction, increasing gray-to-white ratio to be close to that of PET measurement. The rCBF values from the two scatter correction were not significantly different, but the triple-energy window technique suffered from increased noise. After scatter correction, rCBF values were in goad agreement with those measured by PET. Conclusion: This study shows little loss in accuracy results from assuming uniform mu map. However, scatter correction is required for the quantitative rCBF values and gray-to-white ratios to approach those of PET. 1/7/44 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06430779 Genuine Article#: YR214 Number of References: 27 Title: Iterative reconstruction of fluorine-18 SPECT using geometric point response correction Author(s): Zeng GSL; Gullberg GT (REPRINT) ; Bai CY; Christian PE; Trisjono F; DiBella EVR; Tanner JW; Morgan HT Corporate Source: UNIV UTAH,DEPT RADIOL, 729 ARAPEEN DR/SALT LAKE CITY//UT/84108 (REPRINT); UNIV UTAH,DEPT RADIOL/SALT LAKE CITY//UT/84108; PICKER INT,/CLEVELAND//OH/ Journal: JOURNAL OF NUCLEAR MEDICINE, 1998, V39, N1 (JAN), P124-130 ISSN: 0161-5505 Publication date: 19980100 Publisher: SOC NUCLEAR MEDICINE INC, 1850 SAMUEL MORSE DR, RESTON, VA 20190-5316 Language: English Document Type: ARTICLE Abstract: This article demonstrates resolution recovery in F-18 SPECT image reconstruction by using an iterative algorithm that corrects for the system geometric response. Methods: Patient and phantom studies were performed using a Picker PRISM 3000 three-detector SPECT system (Picker International, Inc., Cleveland, OH) to image F-18 With 511 keV collimators. A measured point response function of the imaging system was used in an iterative reconstruction algorithm in which the projector and backprojector modeled the system point response function by using an efficient layer-by-layer blurring technique. The blurring function was a five-element kernel in the shape of a cross. The iterative reconstruction algorithm was an ordered-subset maximum-likelihood expectation maximization algorithm. Results: The iterative reconstruction algorithm with geometric response correction showed an improvement in resolution over the filtered backprojection reconstruction and the iterative reconstruction without correction. Conclusion: The proposed iterative reconstruction algorithm with geometric response correction is efficient and effective with significant resolution recovery. 1/7/45 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06400445 Genuine Article#: YP958 Number of References: 39 Title: Duel matrix ordered subsets reconstruction for accelerated 3D scatter compensation in single-photon emission tomography Author(s): Kamphuis C (REPRINT) ; Beekman FJ; vanRijk PP; Viergever MA Corporate Source: UNIV UTRECHT HOSP,IMAGE SCI INST, E02-222, HEIDELBERGLAAN 100/NL-3584 CX UTRECHT//NETHERLANDS/ (REPRINT) Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1998, V25, N1 (JAN), P8-18 ISSN: 0340-6997 Publication date: 19980100 Publisher: SPRINGER VERLAG, 175 FIFTH AVE, NEW YORK, NY 10010 Language: English Document Type: ARTICLE Abstract: Three-dimensional (3D) iterative maximum likelihood expectation maximization (ML-EM) algorithms for single-photon emission tomography (SPET) are capable of correcting image-degrading effects of non-uniform attenuation, distance-dependent camera response and patient shape-dependent scatter. However, the resulting improvements in quantitation, resolution and signal-to-noise ratio (SNR) are obtained at the cost of a huge computational burden. This paper presents a new acceleration method for ML-EM: dual matrix ordered subsets (DM-OS). DM-OS combines two acceleration methods: (a) different matrices for projection and back-projection and (b) ordered subsets of projections. DM-OS was compared with ML-EM on simulated data and on physical thorax phantom data, for both 180 degrees and 360 degrees orbits. Contrast, normalized standard deviation and mean squared error were calculated for the digital phantom experiment. DM-OS resulted in similar image quality to ML-EM, even for speed-up factors of 200 compared to ML-EM in the case of 120 projections. The thorax phantom data could be reconstructed 50 times faster (60 projections) using DM-OS with preservation of image quality. ML-EM and DM-OS with scatter compensation showed significant improvement of SNR compared to ML-EM without scatter compensation. Furthermore, inclusion of complex image formation models in the computer code is simplified in the case of DM-OS. It is thus shown that DM-OS is a fast and relatively simple algorithm for 3D iterative scatter compensation, with similar results to conventional ML-EM, for both 180 degrees and 360 degrees acquired data. 1/7/46 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06372022 Genuine Article#: YM900 Number of References: 38 Title: Accelerating the EMML algorithm and related iterative algorithms by rescaled block-iterative methods Author(s): Byrne CL (REPRINT) Corporate Source: UNIV LOWELL,DEPT MATH SCI/LOWELL//MA/01854 (REPRINT) Journal: IEEE TRANSACTIONS ON IMAGE PROCESSING, 1998, V7, N1 (JAN), P 100-109 ISSN: 1057-7149 Publication date: 19980100 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Analysis of convergence of the algebraic reconstruction technique (ART) shows it to be predisposed to converge to a solution faster than simultaneous methods, such as those of the Cimmino-Landweber type, the expectation maximization maximum likelihood method for the Poisson model (EMML), and the simultaneous multiplicative ART (SMART), which use all the data at each step, Although choice of ordering of the data and of relaxation parameters are important, as Herman and Meyer have shown, they are not the full story, The analogous multiplicative ART (MART), which applies only to systems y = Pr in which y > 0, P greater than or equal to 0 and a nonnegative solution is sought, is also sequential (or ''row-action''), rather than simultaneous, but does not generally exhibit the same accelerated convergence relative to its simultaneous version, SMART. By dividing each equation by the maximum of the corresponding row of P, we find that this rescaled MART (RMART) does converge faster, when solutions exist, significantly so in cases in which the row maxima are substantially less than one, Such cases arise frequently in tomography and when the columns of P have been normalized to have sum one. Between simultaneous methods, which use all the data at each step, and sequential (or row-action) methods, which use only a single data value at each step, there are the block-iterative (or ordered subset) methods, in which a single block or subset of the data is processed at each step. The ordered subset EM (OSEM) of Hudson et al, is significantly faster than the EMML, but often fails to converge. The ''rescaled block-iterative'' EMML RBI-EMML) is an accelerated block-iterative version of EMML that converges, in the consistent case, to a solution, for any choice of subsets; it reduces to OSEM when the restrictive ''subset balanced'' condition holds, Rescaled block-iterative versions of SMART and MART also exhibit accelerated convergence. 1/7/47 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06365147 Genuine Article#: YM433 Number of References: 18 Title: Monte Carlo evaluation of accuracy and noise properties of two scatter correction methods for Tl-201 cardiac SPECT Author(s): Narita Y (REPRINT) ; Iida H; Eberl S; Nakamura T Corporate Source: RES INST BRAIN & BLOOD VESSELS,DEPT RADIOL & NUCL MED, 6-10 SENSHU KUBOTA MACHI/AKITA 010//JAPAN/ (REPRINT); ROYAL PRINCE ALFRED HOSP,PET & NUCL MED DEPT/CAMPERDOWN/NSW 2050/AUSTRALIA/; TOHOKU UNIV,CTR CYCLOTRON & RADIOISOTOPE, AOBA KU/SENDAI/MIYAGI 98022/JAPAN/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1997, V44, N6,2 (DEC), P 2465-2472 ISSN: 0018-9499 Publication date: 19971200 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Two independent scatter correction techniques, transmission dependent convolution subtraction (TDCS) and triple-energy window (TEW) method, were evaluated in terms of quantitative accuracy and noise properties using Monte Carlo simulation (EGS4). Emission projections (primary, scatter and scatter plus primary) were simulated for three numerical phantoms for Tl-201. Data were reconstructed with ordered-subset EM algorithm including noise-less transmission data based attenuation correction. Accuracy of TDCS and TEW scatter corrections were assessed by comparison with simulated true primary data The uniform cylindrical phantom simulation demonstrated better quantitative accuracy with TDCS than with TEW (-2.0% vs 16.7%) and better S/N (6.48 vs 5.05). A uniform ring myocardial phantom simulation demonstrated better homogeneity with TDCS than TEW in the myocardium; i.e., anterior-to-posterior wall count ratios were 0.99 and 0.76 with TDCS and TEW, respectively. For the MCAT phantom, TDCS provided good visual and quantitative agreement with simulated true primary image without noticeably increasing the noise after scatter correction. Overall TDCS proved to be more accurate and less noisy than TEW, facilitating quantitative assessment of physiological functions with SPECT. 1/7/48 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06365137 Genuine Article#: YM433 Number of References: 21 Title: Optimization of transmission and emission scan duration in 3D whole-body PET Author(s): Beyer T (REPRINT) ; Kinahan PE; Townsend DW Corporate Source: UNIV PITTSBURGH,MED CTR, PET FACIL, 200 LOTHROP ST/PITTSBURGH//PA/15213 (REPRINT) Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1997, V44, N6,2 (DEC), P 2400-2407 ISSN: 0018-9499 Publication date: 19971200 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Whole-body PET imaging is being increasingly used to identify and localize malignant disease remote from the site of the primary tumour. Patients are typically scanned at multiple contiguous bed positions over an axial length of 75-100 cm. Ideally, for oncology patients, the total scan duration should not exceed about an hour and therefore only 5-10 minutes of imaging can be performed at each bed position. To minimize the total scan duration, the transmission scan is often omitted and the emission scan reconstructed without attenuation correction. However, whole-body scans reconstructed without attenuation are non-quantitative and can lead to incorrect diagnoses, particularly for tumours located deep within the body. We have performed a series of torso phantom measurements on a 3D PET scanner (ECAT ART) to investigate the optimal partition of scan time between the emission and transmission scans for a fixed total scan duration. We find that 20%-40% of the total scan time should be dedicated to the transmission acquisition to minimize noise in the attenuation-corrected image. The optimal partition depends on the method of calculating the attenuation correction factors and on the reconstruction algorithm. 1/7/49 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06364695 Genuine Article#: YM434 Number of References: 28 Title: Influence of OSEM, elliptical orbits and background activity on SPECT 3D resolution recovery Author(s): Pan TS; Luo DS; Kohli V; King MA (REPRINT) Corporate Source: UNIV MASSACHUSETTS,MED CTR, 55 LAKE AVE N/WORCESTER//MA/01655 (REPRINT); UNIV MASSACHUSETTS,MED CTR/WORCESTER//MA/01655 Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1997, V42, N12 (DEC), P2517-2529 ISSN: 0031-9155 Publication date: 19971200 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: In maximum-likelihood expectation-maximization (MLEM) reconstruction of SPECT images, if both attenuation correction (AC) and detector response correction (DRC) are included, the reconstruction can be too time consuming to be clinically useful. With use of the ordered-subset expectation-maximization (OSEM) reconstruction, it has been reported that the reconstruction time can be substantially reduced. We investigated the reconstruction of point sources in a non-uniform attenuation medium in terms of the normalized FWHM of these sources. We compared MLEM versus OSEM reconstructions; circular versus elliptical orbits; and the presence versus the absence of background activity in the object. We found: (i) that OSEM does speed up the reconstruction by a factor of 10 over MLEM; (ii) that the resolution recovery does not depend on the type of orbit if both AC and DRC are included in the reconstruction; however, when there is background activity, a significant number of iterations are required to alleviate the effect of orbit; (iii) that background activity significantly slows down the resolution recovery of the point sources; and (iv) that if reconstruction only includes AC, and not DRC, changing orbit can change isotropy of recovered resolution, whereas introducing background activity may degrade the recovered resolution and also changes the isotropy. 1/7/50 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06364692 Genuine Article#: YM434 Number of References: 30 Title: Dedicated PET scanners for breast imaging Author(s): Freifelder R (REPRINT) ; Karp JS Corporate Source: UNIV PENN,DEPT RADIOL, 110 DONNER, 3400 SPRUCE ST/PHILADELPHIA//PA/19104 (REPRINT) Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1997, V42, N12 (DEC), P2463-2480 ISSN: 0031-9155 Publication date: 19971200 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: We have used computer simulations to compare two designs for a PET scanner dedicated to breast imaging with a whole-body PET scanner. The new designs combine high spatial resolution, high sensitivity, and good energy resolution to detect small, low-contrast masses. The detectors are position sensitive NaI(T1) scintillators. The first design is a ring scanner surrounding the breast and the second consists of two planar detectors placed on opposite sides of the breast. We have employed standard performance measures to compare the different designs: contrast, percentage standard deviation of the background, and signal-to-noise ratios of reconstructed images. The results of the simulations show that both of the proposed designs have better lesion detectability than a whole-body scanner. The results also show that contrast is higher in the ring breast system but that the noise is lower in the planar breast system. Overall, the ring system yields images with the best signal-to-noise ratios, although the planar system offers practical advantages for imaging the breast and axilla. 1/7/51 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06345074 Genuine Article#: YK851 Number of References: 18 Title: Simultaneous emission transmission tomography using technetium-99m for both emission and transmission Author(s): Barnden LR (REPRINT) ; Ong PL; Rowe CC Corporate Source: QUEEN ELIZABETH HOSP,DEPT NUCL MED/WOODVILLE/SA 5011/AUSTRALIA/ (REPRINT) Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1997, V24, N11 (NOV), P 1390-1397 ISSN: 0340-6997 Publication date: 19971100 Publisher: SPRINGER VERLAG, 175 FIFTH AVE, NEW YORK, NY 10010 Language: English Document Type: ARTICLE Abstract: This phantom study investigates whether attenuation maps from transmission data degraded by increased noise from subtraction of emission counts can still provide useful attenuation correction in the regular and obese chest. Technetium-99m was used for both emission and transmission on a triple head simultaneous emission transmission tomography (Tc-Tc SETT) system, Fanbeam transmission counts were computed by subtracting emission counts estimated from the two parallel collimator heads, Radioactive decay was used to simulate organ counts from injections of 900 and 400 MBq sestamibi for regular and obese chest sizes. Line source activity was 350 MBq, Control attenuation maps were obtained with no emission activity, Noise control included catering for negative and zero transmission counts, pre-filtering and segmentation of mu maps, Pre-filtering was tried before and after subtraction and before and after setting negative pixels to zero, Mean+/-SD count/pixel at the heart in anterior transmission projections was typically 33+/-18 for the regular and 1+/-7 for the obese chest. For the obese chest, pre-filtering before resetting negative counts best preserved mean mu in soft tissue and lung, Tc-Tc SETT mu mean+/-SD for the regular chest were 0.144+/-0.012 and 0.058+/-0.004 for soft tissue and lung and for the obese chest, 0.152+/-0.075 and 0.059+/-0.017, The accuracy of the Tc-Tc SETT bullseye plots for the regular chest was the same as with control map attenuation correction and 3 times better than with no correction. For the obese chest it was as good as with control map correction only if mu mu map segmentation was applied. Tc-Tc SETT soft tissue and lung mu in 28 patient studies indicated that segmentation is practical for a wide range of chest sizes, Tc-Tc SETT on a triple-head system offers an accurate, inexpensive method of attenuation correction for the majority of chest sizes. 1/7/52 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06333803 Genuine Article#: YK067 Number of References: 73 Title: SPECT quantification: a review of the different correction methods with Compton scatter, attenuation and spatial deterioration effects. Author(s): Groiselle C; deDreuille O; Rocchisani JM; Bendriem B; Gaillard JF; Moretti JL Corporate Source: HOP AVICENNE,NUCL MED SERV/F-93009 BOBIGNY//FRANCE/; HIA VAL DE GRACE,NUCL MED SERV/F-75230 PARIS 05//FRANCE/; CEA,SERV HOSP FREDERIC JOLIOT/F-91406 ORSAY//FRANCE/ Journal: MEDECINE NUCLEAIRE, 1997, V21, N7 (OCT), P397-408 ISSN: 0928-1258 Publication date: 19971000 Publisher: EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 141 RUE JAVEL, 75747 PARIS, FRANCE Language: French Document Type: REVIEW Abstract: The improvement of gamma-cameras, acquisition and reconstruction software opens new perspectives in term of image quantification in nuclear medicine. In order to meet the challenge, numerous works have been undertaken in recent years to correct for the different physical phenomena that prevent an exact estimation of the radioactivity distribution. The main phenomena that have to be taken into account are scatter, attenuation and resolution. In this work, authors present the physical basis of each issue, its consequences on quantification and the main methods proposed to correct them. 1/7/53 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06174760 Genuine Article#: XZ766 Number of References: 35 Title: Improved resolution for PET volume imaging through three-dimensional iterative reconstruction Author(s): Liow JS (REPRINT) ; Strother SC; Rehm K; Rottenberg DA Corporate Source: UNIV MINNESOTA,VET ADM MED CTR, DEPT RADIOL, 1 VET DR/MINNEAPOLIS//MN/55147 (REPRINT); UNIV MINNESOTA,VET ADM MED CTR, DEPT NEUROL/MINNEAPOLIS//MN/55147 Journal: JOURNAL OF NUCLEAR MEDICINE, 1997, V38, N10 (OCT), P1623-1631 ISSN: 0161-5505 Publication date: 19971000 Publisher: SOC NUCLEAR MEDICINE INC, 1850 SAMUEL MORSE DR, RESTON, VA 20190-5316 Language: English Document Type: ARTICLE Abstract: It has been demonstrated that in two-dimensional iterative reconstruction, a resolution model can improve image resolution while controlling noise. With the lower noise levels of three-dimensional PET volume imaging, these iterative reconstruction advantages may be extended to three dimensions to further improve the reconstructed image resolution. Methods: We have implemented three-dimensional versions of iterative filtered backprojection (IFBP) and the maximum likelihood by expectation maximization (ML-EM) reconstruction algorithms and applied them to three-dimensional PET volume datasets, The results were compared to images obtained using the standard three-dimensional reprojection reconstruction (3DRP) algorithm. Results: For IFBP with 15 iterations and no regularization compared to 3DRP, both using a ramp filter, the transaxial resolution improved 52%, and the axial resolution improved 39%, With a strong regularization, the transaxial and axial resolution improvements were reduced to 6% and 5%, respectively. If a Hanning roll-off is applied to the ramp filter in the transaxial direction, the transaxial resolution for IFBP without regularization improved 35% compared lo 3DRP; with regularization the improvement dropped to 19%. The axial resolution for IFBP and 3DRP was unaffected by this transaxial smoothing in the reconstruction filter, With the same Hanning roll-off, the noise for IFBP without regularization increased by a factor of 6 compared to 3DRP; with regularization the noise was increased only by a factor of 3. Compared to IFBP, the three-dimensional ML-EM reconstruction produced similar resolution improvements with a much smaller increase in noise and slower convergence. Resolution improvements from both IFBP and ML-EM reconstructions are visually apparent in three-dimensional FDG brain images and result in increased activation signals in a three-dimensional [O-15]water functional activation study. Conclusion: Our results demonstrate that resolution improvement is possible for IFBP and ML-EM compared to 3DRP with or without noise increase. 1/7/54 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06090481 Genuine Article#: XU583 Number of References: 25 Title: Convergent block-iterative algorithms for image reconstruction from inconsistent data Author(s): Byrne CL (REPRINT) Corporate Source: UNIV LOWELL,DEPT MATH SCI/LOWELL//MA/01854 (REPRINT) Journal: IEEE TRANSACTIONS ON IMAGE PROCESSING, 1997, V6, N9 (SEP), P 1296-1304 ISSN: 1057-7149 Publication date: 19970900 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: It has been shown recently that convergence to a solution can be significantly accelerated for a number of iterative image reconstruction algorithms, including simultaneous Cimmino-type algorithms, the ''expectation maximization'' method for maximizing likelihood (EMML) and the simultaneous multiplicative algebraic reconstruction technique (SMART), through the use of rescaled block-iterative (BI) methods, These BI methods involve partitioning the data into disjoint subsets and using only one subset at each step of the iteration, One drawback of these methods is their failure to converge to an approximate solution in the inconsistent case, in which no image consistent with the data exists; they are always observed to produce limit cycles (LC's) of distinct images, through which the algorithm cycles, No one of these images provides a suitable solution, in general. The question that arises then is whether or not these LC vectors retain sufficient information to construct from them a suitable approximate solution; we show here that they do. To demonstrate that, we employ a ''feedback'' technique in which the LC vectors are used to produce a new ''data'' vector, and the algorithm restarted. Convergence of this nested iterative scheme to an approximate solution is then proven, Preliminary work also suggests that this feedback method may be incorporated in a practical reconstruction method. 1/7/55 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06037138 Genuine Article#: XQ914 Number of References: 33 Title: Scatter compensation methods in 3D iterative SPECT reconstruction: A simulation study Author(s): Beekman FJ (REPRINT) ; Kamphuis C; Frey EC Corporate Source: UNIV UTRECHT HOSP,IMAGE SCI INST/NL-3584 CX UTRECHT//NETHERLANDS/ (REPRINT); UNIV N CAROLINA,DEPT BIOMED ENGN/CHAPEL HILL//NC/27599; UNIV N CAROLINA,DEPT RADIOL/CHAPEL HILL//NC/27599 Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1997, V42, N8 (AUG), P1619-1632 ISSN: 0031-9155 Publication date: 19970800 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: Effects of different scatter compensation methods incorporated in fully 3D iterative reconstruction are investigated. The methods are: (i) the inclusion of an 'ideal scatter estimate' (ISE); (ii) like (i) but with a noiseless scatter estimate (ISE-NF); (iii) incorporation of scatter in the point spread function during iterative reconstruction ('ideal scatter model', ISM); (iv) no scatter compensation (NSC); (v) ideal scatter rejection (ISR), as can be approximated by using a camera with a perfect energy resolution. The iterative method used was an ordered subset expectation maximization (OS-EM) algorithm. A cylinder containing small cold spheres was used to calculate contrast-to-noise curves. For a brain study, global errors between reconstruction and 'true' distributions were calculated. Results show that ISR is superior to all other methods. In all cases considered, ISM is superior to ISE and performs approximately as well as (brain study) or better than (cylinder data) ISE-NF. Both ISM and ISE improve contrast-to-noise curves and reduce global errors, compared with NSC. In the case of ISE, blurring of the scatter estimate with a Gaussian kernel results in slightly reduced errors in brain studies, especially at low count levels. The optimal Gaussian kernel size is strongly dependent on the noise level. 1/7/56 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06022791 Genuine Article#: XP919 Number of References: 7 Title: PET with F-18-fluoride: Effects of iterative versus filtered backprojection reconstruction on kinetic modeling Author(s): Schiepers C (REPRINT) ; Nuyts J; Wu HM; Verma RC Corporate Source: OLIVE VIEW UCLA MED CTR,14445 OLIVE VIEW DR/SYLMAR//CA/91342 (REPRINT); KATHOLIEKE UNIV LEUVEN,/B-3001 LOUVAIN//BELGIUM/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1997, V44, N4,1 (AUG), P 1591-1593 ISSN: 0018-9499 Publication date: 19970800 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: High focal uptake in patients poses particular problems in PET imaging. Filtered backprojection (FBP) introduces disturbing streak artifacts, adversely affecting the identification of structures and delineation of regions. Iterative reconstruction methods (MLEM) provide images of superb quality, however, the accuracy of quantitative results obtained from MLEM images has nor been established for clinical data. Dynamic images were acquired over 1 hr with PET and F-18-fluoride in 6 patients with an old unilateral hip fracture. FBP and MLEM reconstruction was performed. Since the bladder was in the FOV and filled up with fluoride, FBP produced streaks hampering region delineation. Bone blood flow (k1) and fluoride influx rate (Ki) were estimated with a 3 compartment model. Analyzed regions (n=190) showed correlation coefficients between FBP and MLEM: 0.88 for k1 and 0.97 for Ki. Affected and normal femoral head regions (n=30) yielded r=0.89 for k1 and r=0.95 for Ki. Variations up to 46% were seen in individual data. Conclusion: in patients MLEM provides superior images at the expense of an increased reconstruction duration. Our procedure appeared acceptable in clinical routine. Quantitative estimates obtained with kinetic modeling from MLEM data were reliable and correlated highly to those obtained with the standard, validated FBP algorithm. 1/7/57 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06017563 Genuine Article#: XP344 Number of References: 72 Title: A clinical perspective of accelerated statistical reconstruction Author(s): Hutton BF (REPRINT) ; Hudson HM; Beekman FJ Corporate Source: WESTMEAD HOSP,DEPT PHYS MED/WESTMEAD/NSW 2145/AUSTRALIA/ (REPRINT); WESTMEAD HOSP,DEPT PHYS MED/SYDNEY/NSW/AUSTRALIA/; WESTMEAD HOSP,DEPT NUCL MED & ULTRASOUND/SYDNEY/NSW/AUSTRALIA/; MACQUARIE UNIV,DEPT STAT/SYDNEY/NSW 2109/AUSTRALIA/; UNIV UTRECHT HOSP,DEPT NUCL MED, IMAGE SCI INST/UTRECHT//NETHERLANDS/ Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1997, V24, N7 (JUL), P 797-808 ISSN: 0340-6997 Publication date: 19970700 Publisher: SPRINGER VERLAG, 175 FIFTH AVE, NEW YORK, NY 10010 Language: English Document Type: ARTICLE Abstract: Although the potential benefits of maximum likelihood reconstruction have been recognised for many years, the technique has only recently found widespread popularity in clinical practice, Factors which have contributed to the wider acceptance include improved models for the emission process, better understanding of the properties of the algorithm and, not least, the practicality of application with the development of acceleration schemes and the improved speed of computers, The objective in this article is to present a framework for applying maximum likelihood reconstruction for a wide range of clinically based problems, The article draws particularly on the experience of the three authors in applying an acceleration scheme involving use of ordered subsets to a range of applications, The potential advantages of statistical reconstruction techniques include: (a) the ability to better model the emission and detection process, in order to make the reconstruction converge to a quantitative image, (b) the inclusion of a statistical noise model which results in better noise characteristics, and (c) the possibility to incorporate prior knowledge about the distribution being imaged, The great flexibility in adapting the reconstruction for a specific model results in these techniques having wide applicability to problems in clinical nuclear medicine. 1/7/58 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 06017549 Genuine Article#: XP344 Number of References: 33 Title: Cardiac single-photon emission tomography: is attenuation correction enough? Author(s): Hutton BF (REPRINT) Corporate Source: WESTMEAD HOSP,DEPT MED PHYS/SYDNEY/NSW 2145/AUSTRALIA/ (REPRINT); WESTMEAD HOSP,DEPT NUCL MED & ULTRASOUND/SYDNEY/NSW 2145/AUSTRALIA/ Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1997, V24, N7 (JUL), P 713-715 ISSN: 0340-6997 Publication date: 19970700 Publisher: SPRINGER VERLAG, 175 FIFTH AVE, NEW YORK, NY 10010 Language: English Document Type: EDITORIAL MATERIAL 1/7/59 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05902637 Genuine Article#: XF300 Number of References: 9 Title: A study of reconstruction accuracy for a cardiac SPECT system with multi-segmental collimation Author(s): Yu DC (REPRINT) ; Chang W; Pan TS Corporate Source: RUSH PRESBYTERIAN ST LUKES MED CTR,1653 W CONGRESS PKWY/CHICAGO//IL/60612 (REPRINT); UNIV MASSACHUSETTS,MED CTR/WORCESTER//MA/01655 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1997, V44, N3,2 (JUN), P 1403-1408 ISSN: 0018-9499 Publication date: 19970600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: To improve the geometric efficiency of cardiac SPECT imaging, we previously proposed to use a multi-segmental collimation with a cylindrical geometry. The proposed collimator consists of multiple parallel-hole collimators with most of the segments directed toward a small central region, where the patient's heart should be positioned. This technique provides a significantly increased detection efficiency for the central region, but at the expense of reduced efficiency for the surrounding region. We have used computer simulations to evaluate the implication of this technique on the accuracy of the reconstructed cardiac images. Two imaging situations were simulated: 1) the heart well placed inside the central region, and 2) the heart shifted and partially outside the central region. A neighboring high-uptake liver was simulated for both imaging situations. The images were reconstructed and corrected for attenuation with ML-EM and OS-EM methods using a complete attenuation map. The results indicate that errors caused by projection truncation are not significant and are not strongly dependent on the activity of the liver when the heart is well positioned within the central region. When the heart is partially outside the central region, hybrid emission data (a combination of high-count projections from the central region and low-count projections from the background region) can be used to restore the activity of the truncated section of the myocardium. However, the variance of the image in the section of the myocardium outside the central region is increased by 2-3 times when 10% of the collimator segments are used to image the background region. 1/7/60 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05902627 Genuine Article#: XF300 Number of References: 16 Title: Region of interest evaluation of SPECT image reconstruction methods using a realistic brain phantom Author(s): Xia WS (REPRINT) ; Glick SJ; Pan TS; Soares EJ; Luo DS Corporate Source: UNIV MASSACHUSETTS,MED CTR, DEPT NUCL MED/WORCESTER//MA/01655 (REPRINT) Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1997, V44, N3,2 (JUN), P 1336-1341 ISSN: 0018-9499 Publication date: 19970600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: A realistic numerical brain phantom, developed by Zubal et al, was used for a region-of-interest evaluation of the accuracy and noise variance of the following SPECT reconstruction methods: 1) Maximum-Likelihood reconstruction using the Expectation-Maximization (ML-EM) algorithm; 2) an EM algorithm using ordered-subsets (OS-EM); 3) a re-scaled block iterative EM algorithm (RBI-EM); and 4) a filtered backprojection algorithm that uses a combination of the Bellini method for attenuation compensation and an iterative spatial blurring correction method using the frequency-distance principle (FDP). The Zubal phantom was made from segmented MRI slices of the brain, so that neuro-anatomical structures are well defined and indexed. Small regions-of-interest (ROIs) from the white matter, grey matter in the center of the brain and grey matter from the peripheral area of the brain were selected for the evaluation. Photon attenuation and distance-dependent collimator blurring were modeled. Multiple independent noise realizations were generated for two different count levels. The simulation study showed that the ROI bias measured for the EM-based algorithms decreased as the iteration number increased, and that the OS-EM and RBI-EM algorithms (16 and 64 subsets were used) achieved the equivalent accuracy of the ML-EM algorithm at about the same noise variance, with much fewer number of iterations. The Bellini-FDP restoration algorithm converged fast and required less computation per iteration. The ML-EM algorithm had a slightly better ROI bias vs. variance trade-off than the other algorithms. 1/7/61 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05902626 Genuine Article#: XF300 Number of References: 11 Title: Singles transmission scans performed post-injection for quantitative whole body PET imaging Author(s): Smith RJ (REPRINT) ; Karp JS; Muehllehner G; Gualtieri E; Benard F Corporate Source: UNIV PENN,DEPT RADIOL, 3400 SPRUCE ST/PHILADELPHIA//PA/19104 (REPRINT); UGM LAB,/PHILADELPHIA//PA/19104 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1997, V44, N3,2 (JUN), P 1329-1335 ISSN: 0018-9499 Publication date: 19970600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: Post-injection singles transmission scanning has been implemented in the septumless PENN PET 240H scanner. The method uses a 6 mCi point transmission source of Cs-137 at the axial center and 36 cm off transaxial center of the camera field of view. Singles transmission scans of 1.8 minutes per bed axial position provide similar scan count densities to 15 minute coincidence transmission scans with a 0.5 mCi Ge-68 rod transmission source. Scatter and emission contamination suppression are achieved by applying a narrow 662 keV transmission photopeak energy window. The residual 511 keV emission contamination constitutes a background of uniform spatial distribution. Accurate and low noise attenuation correction is achieved by segmenting the singles transmission images into lung and soft tissue volumes. Established 511 keV gamma ray attenuation coefficients are then applied and these images are forward projected for attenuation correction. Expectation maximisation with ordered subsets (OS-EM) reconstruction is performed for the emission data to improve image quality. Both the segmentation and OS-EM reconstruction maintain quantitative accuracy in the fully corrected emission images compared to measured coincidence transmission correction. Thus, a clinical protocol involving 40 minutes of emission scans followed by 20 minutes of singles transmission scans allow the 60 cm of the human torso to be fully scanned within 60 minutes. These quantitative whole body FDG PET images may then be used for tumor grading and assessment of tumor response to treatment. 1/7/62 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05902625 Genuine Article#: XF300 Number of References: 14 Title: Attenuation correction strategies for multi-energy photon emitters using SPECT. Author(s): Pretorius PH (REPRINT) ; King MA; Pan TS; Hutton BF Corporate Source: UNIV MASSACHUSETTS,MED CTR, DEPT NUCL MED, 55 LAKE AVE N/WORCESTER//MA/01655 (REPRINT); UNIV ORANGE FREE STATE,DEPT BIOPHYS/BLOEMFONTEIN//SOUTH AFRICA/; WESTMEAD HOSP,DEPT MED PHYS/WESTMEAD/NSW 2145/AUSTRALIA/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1997, V44, N3,2 (JUN), P 1323-1328 ISSN: 0018-9499 Publication date: 19970600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: The aim of this study nas to investigate whether the photopeak window projections from different energy photons can be combined into a single window for reconstruction or if it is better to not combine the projections due to differences in the attenuation maps required for each photon energy. The mathematical cardiac torso (MCAT) phantom was modified to simulate the uptake of Ga-67 in the human body. Four spherical hot tumors were placed in locations which challenged attenuation correction. An analytical 3D projector with attenuation and detector response included was used to generate projection sets. Data were reconstructed using filtered backprojection (FBP) reconstruction with Butterworth filtering in conjunction with one iteration of Chang attenuation correction, and with 5 and 10 iterations of ordered-subset maximum-likelihood expectation-maximization (ML-OS) reconstruction. To serve as a standard for comparison, the projection sets obtained from the two energies were first reconstructed separately using their own attenuation maps. The emission data obtained from both energies were added and reconstructed using the following attenuation strategies: 1) the 93 keV attenuation map for attenuation correction, 2) the 185 keV attenuation map for attenuation correction, 3) using a weighted mean obtained from combining the 93 keV and 185 keV maps, and 4) an ordered subset approach which combines both energies. The central count ratio (CCR) and total count ratio (TCR) were used to compare the performance of the different strategies. Compared to the standard method, results indicate an overestimation with strategy 1, an under-estimation with strategy 2 and comparable results with strategies 3 and 4. In all strategies, the CCR's of sphere 4 (in proximity to the liver, spleen and backbone) were under-estimated, although TCR's were comparable to that of the other locations. The weighted mean and ordered subset strategies for attenuation correction were of comparable accuracy to reconstruction of the windows separately. They are recommended for multi-energy photon SPECT imaging quantitation when there is a need to combine the acquisitions of multiple windows. This work can also be extended to include other multi-energy photon emitters such as In-111. 1/7/63 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05902622 Genuine Article#: XF300 Number of References: 16 Title: Evaluation of 3D reconstruction algorithms for a small animal PET camera Author(s): Johnson CA (REPRINT) ; Seidel J; Carson RE; Gandler WR; Sofer A; Green MV; DaubeWitherspoon ME Corporate Source: NIH,DIV COMP RES & TECHNOL/BETHESDA//MD/20892 (REPRINT); NIH,DEPT NUCL MED, CTR CLIN/BETHESDA//MD/20892; NIH,PET DEPT, CTR CLIN/BETHESDA//MD/20892; GEORGE MASON UNIV,/FAIRFAX//VA/22030 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1997, V44, N3,2 (JUN), P 1303-1308 ISSN: 0018-9499 Publication date: 19970600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: The use of paired, opposing position-sensitive phototube scintillation cameras (SCs) operating in coincidence for small animal imaging with positron emitters is currently under study. Because of the low sensitivity of the system even in 3D mode and the need to produce images with high resolution, it was postulated that a 3D expectation maximization (EM) reconstruction algorithm might be well suited for this application. We investigated six reconstruction algorithms for the 3D SC PET camera: 2D filtered back-projection (FBP), 3D reprojection (3DRP), 2D EM, 3D EM, 2D ordered subset EM (OSEM), and 3D OSEM. Noise was assessed for all slices by the coefficient of variation in a simulated uniform cylinder. Resolution was assessed from a simulation of 15 point sources in the warm background of the uniform cylinder. At comparable noise levels, the resolution achieved with EM and OSEM (0.9-mm to 1.2-mm) is significantly better than that obtained with FBP or 3DRP (1.5-mm to 2.0-mm.) Images of a rat skull labeled with F-18-fluoride suggest that 3D EM and 3D OSEM can improve image quality of a small animal PET camera. 1/7/64 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05902595 Genuine Article#: XF300 Number of References: 26 Title: An investigation of the filtering of TEW scatter estimates used to compensate for scatter with ordered subset reconstructions Author(s): King MA (REPRINT) ; deVries DJ; Pan TS; Pretorius PH; Case JA Corporate Source: UNIV MASSACHUSETTS,MED CTR, DEPT NUCL MED, 55 LAKE AVE N/WORCESTER//MA/01655 (REPRINT); UNIV ORANGE FREE STATE,DEPT BIOPHYS/BLOEMFONTEIN//SOUTH AFRICA/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1997, V44, N3,2 (JUN), P 1140-1145 ISSN: 0018-9499 Publication date: 19970600 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: With the Triple Energy Window (TEW) scatter correction method, scatter is estimated by interpolation between narrow energy windows placed on either side (or from a single window just below) the photopeak window. The use of narrow windows results in a noisy estimate which requires filtering to prevent significant amplification of noise in the corrected images. Using Monte Carlo simulated projections of a digital model of the anatomy of the torso, we investigated two-dimensional pre-reconstruction filtering of the scatter estimate by the Wiener low-pass filter, and Butterworth low-pass filters with various cutoff frequencies. The scatter estimate was either subtracted from the photopeak window projection or used directly in ordered-subset maximum-likelihood (OS-ML) reconstruction. Using the normalized mean square error (NMSE) between the estimated and true slices as the criterion, it was observed that: 1) low-pass filtering of the TEW scatter estimate dramatically decreases the NMSE compared to that of no filtering of this estimate; 2) the cutoff frequency of the Butterworth filter used to filter the scatter estimate is lower than that typically used for photopeak window images; 3) the cutoff frequency of the Butterworth filter has a broad range of values over which the NMSE is near its minimum value; 4) the cutoff frequency at which the Butterworth reaches its minimum value depends on the number of counts in the TEW window(s), and source distribution; 5) the Wiener low-pass filter adapts to produce a low, but not necessarily the minimum, NMSE; and 6) the inclusion of the scatter estimate directly into OS-ML reconstruction results in a lower NMSE than subtraction of the scatter estimate from the photopeak window prior to reconstruction. 1/7/65 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05873816 Genuine Article#: XD527 Number of References: 129 Title: The EM algorithm - An old folk-song sung to a fast new tune - Discussion Author(s): Rubin DB (REPRINT) ; Titterington DM; Gilks WR; Diebolt J; Aitkin M; Smith CAB; Hinde J; Kent JT; Tyler DE; Damien P; Walker S; Chauveau D; Draper D; Dupuis JA; Fessler J; Gelman A; Green PJ; Hero AO ; Lavielle M; Liu CH; Liu JS; Roberts GO; Sahu SK; Torsney B; Zaslavsky AM Corporate Source: HARVARD UNIV,/CAMBRIDGE//MA/02138 (REPRINT); UNIV GLASGOW,/GLASGOW G12 8QQ/LANARK/SCOTLAND/; MRC,BIOSTAT UNIT/CAMBRIDGE CB2 2BW//ENGLAND/; UNIV GRENOBLE,/GRENOBLE//FRANCE/; UNIV NEWCASTLE,/NEWCASTLE UPON TYNE/TYNE & WEAR/ENGLAND/; UNIV COLL LONDON,/LONDON WC1E 6BT//ENGLAND/; UNIV EXETER,/EXETER EX4 4QJ/DEVON/ENGLAND/; UNIV LEEDS,/LEEDS LS2 9JT/W YORKSHIRE/ENGLAND/; RUTGERS STATE UNIV,/PISCATAWAY//NJ/08855; UNIV MICHIGAN,/ANN ARBOR//MI/48109; UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,/LONDON SW7 2AZ//ENGLAND/; UNIV MARNE VALLEE,/NOISY LE GRAND//FRANCE/; UNIV BATH,/BATH BA2 7AY/AVON/ENGLAND/; UNIV TOULOUSE 3,/F-31062 TOULOUSE//FRANCE/; COLUMBIA UNIV,/NEW YORK//NY/10027; UNIV BRISTOL,/BRISTOL BS8 1TH/AVON/ENGLAND/; UNIV PARIS 05,/PARIS//FRANCE/; AT&T BELL LABS,/MURRAY HILL//NJ/07974; STANFORD UNIV,/STANFORD//CA/94305; UNIV CAMBRIDGE,/CAMBRIDGE CB2 1TN//ENGLAND/; HARVARD UNIV,SCH MED/BOSTON//MA/ Journal: JOURNAL OF THE ROYAL STATISTICAL SOCIETY SERIES B-METHODOLOGICAL, 1997, V59, N3, P541-567 ISSN: 0035-9246 Publication date: 19970000 Publisher: BLACKWELL PUBL LTD, 108 COWLEY RD, OXFORD, OXON, ENGLAND OX4 1JF Language: English Document Type: EDITORIAL MATERIAL 1/7/66 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05872985 Genuine Article#: XD503 Number of References: 25 Title: The direct calculation of parametric images from dynamic PET data using maximum-likelihood iterative reconstruction Author(s): Matthews J (REPRINT) ; Bailey D; Price P; Cunningham V Corporate Source: HAMMERSMITH HOSP,MRC, CYCLOTRON UNIT, PET ONCOL GRP, CLIN SCI CTR/LONDON W12 0HS//ENGLAND/ (REPRINT); HAMMERSMITH HOSP,MRC, CYCLOTRON UNIT, PET METHODOL GRP, CLIN SCI CTR/LONDON W12 0HS//ENGLAND/ Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1997, V42, N6 (JUN), P1155-1173 ISSN: 0031-9155 Publication date: 19970600 Publisher: IOP PUBLISHING LTD, DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE Language: English Document Type: ARTICLE Abstract: The aim of this work is to calculate, directly from projection data, concise images characterizing the spatial and temporal distribution of labelled compounds from dynamic PET data. Conventionally, image reconstruction and the calculation of parametric images are performed sequentially. By combining the two processes, low-noise parametric images are obtained, using a computationally feasible parametric iterative reconstruction (PIR) algorithm. PIR is performed by restricting the pixel time-activity curves to a positive linear sum of predefined time characteristics. The weights in this sum are then calculated directly from the PET projection data, using an iterative algorithm based on a maximum-likelihood iterative algorithm commonly used for tomographic reconstruction. The ability of the algorithm to extract known kinetic components from the raw data is assessed, using data from both a phantom experiment and clinical studies. The calculated parametric images indicate differential kinetic behaviour and have been used to aid in the identification of tissues which exhibit differences in the handling of labelled compounds. These parametric images should be helpful in defining regions of interest with similar functional behaviour, and with FDG Patlak analysis. 1/7/67 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05784546 Genuine Article#: WX349 Number of References: 11 Title: High-performance computing and networking as tools for accurate emission computed tomography reconstruction Author(s): Passeri A; Formiconi AR (REPRINT) ; DeCristofaro MTR; Pupi A; Meldolesi U Corporate Source: UNIV FLORENCE,SEZ MED NUCL, DIPARTIMENTO FISIOPATOL CLIN, VIALE MORGAGNI 85/I-50134 FLORENCE//ITALY/ (REPRINT); UNIV FLORENCE,SEZ MED NUCL, DIPARTIMENTO FISIOPATOL CLIN/I-50134 FLORENCE//ITALY/ Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1997, V24, N4 (APR), P 390-397 ISSN: 0340-6997 Publication date: 19970400 Publisher: SPRINGER VERLAG, 175 FIFTH AVE, NEW YORK, NY 10010 Language: English Document Type: ARTICLE Abstract: It is well known that the quantitative potential of emission computed tomography (ECT) relies on the ability to compensate for resolution, attenuation and scatter effects. Reconstruction algorithms which are able to take these effects into account are highly demanding in terms of computing resources, The reported work aimed to investigate the use of a parallel high-performance computing platform for ECT reconstruction taking into account an accurate model of the acquisition of single-photon emission tomographic (SPET) data. An iterative algorithm with an accurate model of the variable system response was ported on the MIMD (Multiple Instruction Multiple Data) parallel architecture of a 64-node Gray T3D massively parallel computer. The system was organized to make it easily accessible even from low-cost PC-based workstations through standard TCP/IP networking. A complete brain study of 30 (64 x 64) slices could be reconstructed from a set of 90 (64 x 64) projections with ten iterations of the conjugate gradients algorithm in 9 s, corresponding to an actual speed-Lip factor of 135, This work demonstrated the possibility of exploiting remote high-performance computing and networking resources from hospital sites by means of low-cost workstations using standard communication protocols without particular problems for routine use. The achievable speed-up factors allow the assessment of the clinical benefit of advanced reconstruction techniques which require a heavy computational burden fur the compensation effects such as variable spatial resolution, scatter and attenuation, The possibility of using the same software on the same hardware platform with data acquired in different laboratories with various kinds of SPET instrumentation is appealing for software quality control and for the evaluation of the clinical impact of the reconstruction methods. 1/7/68 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05711210 Genuine Article#: WR356 Number of References: 15 Title: Bayesian image reconstruction for emission tomography based on median root prior Author(s): Alenius S; Ruotsalainen U (REPRINT) Corporate Source: TURKU PET CTR,/FIN-20520 TURKU//FINLAND/ (REPRINT); TURKU PET CTR,/FIN-20520 TURKU//FINLAND/; TAMPERE UNIV TECHNOL,SIGNAL PROC LAB/FIN-33101 TAMPERE//FINLAND/ Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1997, V24, N3 (MAR), P 258-265 ISSN: 0340-6997 Publication date: 19970300 Publisher: SPRINGER VERLAG, 175 FIFTH AVE, NEW YORK, NY 10010 Language: English Document Type: ARTICLE Abstract: The aim of the present study was to investigate a new type of Bayesian one-step late reconstruction method which utilizes a median root prior (MRP). The method favours images which have locally monotonous radioactivity concentrations. The new reconstruction algorithm was applied to ideal simulated data, phantom data and some patient examinations with PET, The same projection data were reconstructed with filtered back-projection (FBP) and maximum likelihood-expectation maximization (ML-EM) methods for comparison, The MRP method provided good-quality images with a similar resolution to the FBP method with a ramp filter, and at the same lime the noise properties were as good as with Hann-filtered FBP images. The typical artefacts seen in FBP reconstructed images outside of the object were completely removed, as was the grainy noise inside the object, Quantitatively, the resulting average regional radioactivity concentrations in a large region of interest in images produced by the MRP method corresponded to the FBP and ML-EM results but st the pixel by pixel level the MRP method proved to be the most accurate of the tested methods. Tn contrast to other iterative reconstruction methods, e.g. ML-EMI the MRP method was not sensitive to the number of iterations nor to the adjustment of reconstruction parameters. Only the Bayes lan parameter beta had to be set. The proposed MRP method is much more simple to calculate than the methods described previously, both with regard to the parameter settings and in terms of general use. The new MRP reconstruction method was shown to produce high-quality quantitative emission images with only one parameter setting in addition to the number of iterations. 1/7/69 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05709227 Genuine Article#: WR587 Number of References: 17 Title: A focus-of-attention preprocessing scheme for EM-ML PET reconstruction Author(s): Gregor J (REPRINT) ; Huff DA Corporate Source: UNIV TENNESSEE,DEPT COMP SCI, 107 AYRES HALL/KNOXVILLE//TN/37996 (REPRINT) Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1997, V16, N2 (APR), P 218-223 ISSN: 0278-0062 Publication date: 19970400 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: LETTER Abstract: The expectation-maximization maximum-likelihood (ER-ML) algorithm belongs to a family of algorithms that compute positron emission tomography (PET) reconstructions bg iteratively solving a large linear system of equations, We describe a preprocessing scheme for automatically focusing the attention, and thus the computational resources, on a subset of the equations and unknowns. Experimental work with a CM-5 parallel computer implementation using a simulated phantom as well as real data obtained from an ECAT 921 PET scanner indicates that quite significant savings can be obtained with respect to both time and space requirements of the EM-ML algorithm without compromising the quality of the reconstructed images. 1/7/70 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05709221 Genuine Article#: WR587 Number of References: 32 Title: Weighted least-squares reconstruction methods for positron emission tomography Author(s): Anderson JMM (REPRINT) ; Mair BA; Rao M; Wu CH Corporate Source: UNIV FLORIDA,DEPT ELECT & COMP ENGN, CSE BLDG 42, POB 116130/GAINESVILLE//FL/32611 (REPRINT); UNIV FLORIDA,DEPT MATH/GAINESVILLE//FL/32611 Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1997, V16, N2 (APR), P 159-165 ISSN: 0278-0062 Publication date: 19970400 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: We present unpenalized and penalized weighted least squares (WLS) reconstruction methods for positron emission tomography (PET), where the weights are based on the covariance of a model error and depend on the unknown parameters, The penalty function for the latter method is chosen so that certain a priori information is incorporated, The algorithms used to minimize the WLS objective functions guarantee nonnegative estimates and, experimentally, they converged faster than the maximum likelihood expectation-maximization (ML-EM) algorithm and produced images that had significantly better resolution and contrast, Although simulations suggest that the proposed algorithms are globally convergent, a proof of convergence has not yet been found, Nevertheless, we are able to show that the unpenalized method produces estimates that decrease the objective function monotonically with increasing iterations. 1/7/71 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05709220 Genuine Article#: WR587 Number of References: 43 Title: Exact and approximate rebinning algorithms for 3-D PET data Author(s): Defrise M (REPRINT) ; Kinahan PE; Townsend DW; Michel C; Sibomana M; Newport DF Corporate Source: FREE UNIV BRUSSELS,AKAD ZIEKENHUIS, DIV NUCL MED, LAARBEEKLAAN 101/B-1090 BRUSSELS//BELGIUM/ (REPRINT); NATL FUND SCI RES,/LOUVAIN//BELGIUM/; UNIV PITTSBURGH,MED CTR, PET FACIL/PITTSBURGH//PA/15260; UNIV CATHOLIQUE LOUVAIN,PET LAB/B-1348 LOUVAIN//BELGIUM/; CTI,/KNOXVILLE//TN/37921 Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1997, V16, N2 (APR), P 145-158 ISSN: 0278-0062 Publication date: 19970400 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: This paper presents two new rebinning algorithms for the reconstruction of three-dimensional (3-D) positron emission tomography (PET) data, A rebinning algorithm is one that first sorts the 3-D data into an ordinary two-dimensional (2-D) data set containing one sinogram for each transaxial slice to be reconstructed; the 3-D image is then recovered by applying to each slice a 2-D reconstruction method such as filtered-backprojection, This approach allows a significant speedup of 3-D reconstruction, which is particularly useful for applications involving dynamic acquisitions or whole-body imaging, The first new algorithm is obtained by discretizing an exact analytical inversion formula, The second algorithm, called the Fourier rebinning algorithm (FORE), is approximate but allows an efficient implementation based on taking 2-D Fourier transforms of the data, This second algorithm was implemented and applied to data acquired with the new generation of PET systems and also to simulated data for a scanner with an 18 degrees axial aperture, The reconstructed images were compared to those obtained with the 3-D reprojection algorithm (3DRP) which is the standard ''exact'' 3-D filtered-backprojection method, Results demonstrate that FORE provides a reliable alternative to 3DRP, while at the same time achieving an order of magnitude reduction in processing time. 1/7/72 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05634535 Genuine Article#: WM303 Number of References: 11 Title: Iterative reconstruction of PET images using a high-overrelaxation single-projection algorithm Author(s): Schmidlin P (REPRINT) ; Bellemann ME; Brix G Corporate Source: DEUTSCH KREBSFORSCHUNGSZENTRUM,FORSCH SCHWERPUNKT RADIOL, NEUENHEIMER FELD 280/D-69120 HEIDELBERG//GERMANY/ (REPRINT) Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1997, V42, N3 (MAR), P569-582 ISSN: 0031-9155 Publication date: 19970300 Publisher: IOP PUBLISHING LTD, TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX Language: English Document Type: ARTICLE Abstract: An iterative image reconstruction procedure is described which is able to calculate high-precision images within eight iterative steps. High initial overrelaxation parameters are used which drop down towards about one during continuing iteration. The parameters are determined pragmatically, postulating maximum gain of image quality during a sequence of iterative steps. Results with simulated and measured data show that parameters derived from one data set may be widely used for other data sets. The acceleration of iterative reconstruction achieved by the estimation of optimum overrelaxation parameters is important for large data sets, especially for fully 3D reconstruction. 1/7/73 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05501573 Genuine Article#: WC905 Number of References: 29 Title: Noise characterization of combined bellini-type attenuation correction andfrequency-distance principle restoration filtering Author(s): Soares EJ (REPRINT) ; Glick SJ; King MA Corporate Source: COLL HOLY CROSS,DEPT MATH/WORCESTER//MA/01610 (REPRINT); UNIV MASSACHUSETTS,MED CTR, DEPT NUCL MED/WORCESTER//MA/01655 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1996, V43, N6,2 (DEC), P 3278-3290 ISSN: 0018-9499 Publication date: 19961200 Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 345 E 47TH ST, NEW YORK, NY 10017-2394 Language: English Document Type: ARTICLE Abstract: In this paper, we investigate how successive processing of the projection data with Bellini-type (BT) attenuation correction, frequency-distance principle (FDP) restoration filtering, and filtered-backprojection (FBP) reconstruction propagates noise into the reconstructed image, The BT methods, which are Fourier-domain correction techniques, are all exact solutions to theattenuated Radon transform under the constraints of uniform attenuation and a convex object contour,The FDP states that points in the object at a specified distance from the center-of-rotation will contribute predominantly to particular regions of the Fourier transform-series expansion of the sinogram, Using this frequency-distance information, the nonstationary response of the collimator can ideally be deconvolved using an inverse filter, In the presence of noise, however, the FDP filter needs to be regularized in order to control noise amplification caused by the deconvolution, The noise ischaracterized by calculating the population covariance matrix of the projection data after successive processing with BT attenuation correction and FDP filtering and of the reconstructed image after FBP reconstruction, This is done for a simulated point-source located near the edge of an elliptical, uniformly attenuating medium, In our study, we consider the two implementational combinations of BT correction and FDP filtering that allow for sequential processing of the projection data, which we cad mirroring and no mirroring, The results show that the mirroring strategy introduces local positive angular noise correlations in the processed sinogram that are caused bysmoothing of the data in the projection angular direction, Furthermore, mirroring highly correlates the noise in opposing projection views. The impact on the image covariance is the presence of positive angular (arc-like) noise correlations, In contrast, the no mirroring strategy yields local positive and negative noise correlations with negative side-lobes in the processed sinogram, Also, no mirroring does not correlate noise in opposing projection views, The result on the image covariance structure is the presence ofpositive and negative angular correlations with negative side-lobes, It was also noted that the no mirroring scenario produces a much higher noise variance relative to the mirroring implementation of BT attenuation correction and FDP filtering. 1/7/74 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05344420 Genuine Article#: VR532 Number of References: 64 Title: MINIMUM CROSS-ENTROPY RECONSTRUCTION OF PET IMAGES USING PRIOR ANATOMICAL INFORMATION Author(s): ARDEKANI BA; BRAUN M; HUTTON BF; KANNO I; IIDA H Corporate Source: RES INST BRAIN & BLOOD VESSELS,DEPT RADIOL & NUCL MED,6-10 SENSHU KUBOTA MACHI/AKITA 010//JAPAN/; UNIV TECHNOL SYDNEY,DEPT APPL PHYS/BROADWAY/NSW2007/AUSTRALIA/; WESTMEAD HOSP,DEPT MED PHYS/WESTMEAD/NSW 2145/AUSTRALIA/ Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1996, V41, N11 (NOV), P2497-2517 ISSN: 0031-9155 Language: ENGLISH Document Type: ARTICLE Abstract: An algorithm is presented for the reconstruction of PET images using prior anatomical information derived from MR images of the same subject. The cross-entropy or Kullback-Leiber distance is a measure of dissimilarity between two images. We propose to reconstruct PET images by minimizing a weighted sum of two cross-entropy terms. The first is the cross-entropy between the measured emission data and the forward projection of the current estimate of the PET image. Minimizing this term alone is equivalent to the ML-EM reconstruction. The second term is the cross-entropy between the current estimate of the PET image and a prior image model which incorporates anatomical information derived from registered MR images. A weighting parameter determines the relative emphasis given to the emission data and the prior model in the reconstruction. Details of this algorithm are presented as well as test reconstructions for real and simulated data. The performance of the algorithm was evaluated with respect to errors in prior anatomical information. The algorithm provided significant improvement in the quality of reconstructed images as compared with the ML-EM reconstruction technique. The reconstructed images had higher resolution as compared with the images obtained from MAP-like reconstructions which do not utilize anatomical information. The algorithm displayed robustness with respect to errors in prior anatomical information. 1/7/75 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05344419 Genuine Article#: VR532 Number of References: 23 Title: MONTE-CARLO AND EXPERIMENTAL EVALUATION OF ACCURACY AND NOISE PROPERTIES OF 2 SCATTER CORRECTION METHODS FOR SPECT Author(s): NARITA Y; EBERL S; IIDA H; HUTTON BF; NAKAMURA T; BAUTOVICH G Corporate Source: RES INST BRAIN & BLOOD VESSELS,DEPT RADIOL & NUCL MED/AKITA//JAPAN/; ROYAL PRINCE ALFRED HOSP,DEPT NUCL MED/SYDNEY/NSW/AUSTRALIA/; WESTMEAD HOSP,DEPT MED PHYS/SYDNEY/NSW/AUSTRALIA/; UNIV TECHNOL SYDNEY,SCH APPL PHYS/SYDNEY/NSW/AUSTRALIA/; TOHOKU UNIV,CTR CYCLOTRON & RADIOISOTOPE/SENDAI/MIYAGI 980/JAPAN/ Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1996, V41, N11 (NOV), P2481-2496 ISSN: 0031-9155 Language: ENGLISH Document Type: ARTICLE Abstract: Scatter correction is a prerequisite for quantitative SPECT, but potentially increases noise. Monte Carlo simulations (EGS4) and physical phantom measurements were used to compare accuracy and noise properties of two scatter correction techniques: the triple-energy window (TEW), and the transmission dependent convolution subtraction (TDCS) techniques. Two scatter functions were investigated for TDCS: (i) the originally proposed mono-exponential function (TDCSmono) and (ii) an exponential plus Gaussian scatter function (TDCSGauss) demonstrated to be superior from our Monte Carlo simulations. Signal to noise ratio (SIN) and accuracy were investigated in cylindrical phantoms and a chest phantom. Results from each method were compared to the true primary counts (simulations), or known activity concentrations (phantom studies). Tc-99m was used in all cases. The optimized TDCSGauss method overall performed best, with an accuracy of better than 4% for all simulations and physical phantom studies. Maximum errors for TEW and TDCSmono of -30 and -22%, respectively, were observed in the heart chamber of the simulated chest phantom. TEW had the worst SIN ratio of the three techniques. The SIN ratios of the two TDCS methods were similar and only slightly lower than those of simulated true primary data. Thus, accurate quantitation can be obtained with TDCSGauss, with a relatively small reduction in S/N ratio. 1/7/76 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05323498 Genuine Article#: VQ008 Number of References: 34 Title: A NONNEGATIVE FAST MULTIPLICATIVE ALGORITHM IN 3D SCATTER-COMPENSATED SPET RECONSTRUCTION Author(s): WALRAND SH; VANELMBT LR; PAUWELS S Corporate Source: UNIV CATHOLIQUE LOUVAIN,CTR MED NUCL,UCL 5430,AVE HIPPOCRATE 54/B-1200 BRUSSELS//BELGIUM/ Journal: EUROPEAN JOURNAL OF NUCLEAR MEDICINE, 1996, V23, N11 (NOV), P 1521-1526 ISSN: 0340-6997 Language: ENGLISH Document Type: ARTICLE Abstract: Single-photon emission tomographic (SPET) reconstruction can be improved, especially for noisy images, by using the iterative expectation-maximization of the maximum-likelihood (EM-ML) algorithm. Its application to clinical routine is, however, hampered by the high number of iterations necessary to achieve acceptable results. Therefore various methods have been developed to accelerate the EM-ML algorithm. In this paper a new accelerated EM-ML-like multiplicative algorithm is proposed for SPET reconstruction. Contrary to some other accelerating methods, it preserves two of the most important properties of the EM-ML, namely pixel positivity inside the patient body and null activity outside. The convergence speed is improved by a factor which can reach 100 in high spatial frequency or low count regions. Good estimates in the low count region are obtained without any smoothing, even at typical routine clinical count rates. The algorithm used in conjunction with the 3D effective one scatter path model provides high-quality SPET images and accurate quantitation. 1/7/77 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05260240 Genuine Article#: VL376 Number of References: 49 Title: A ROW-ACTION ALTERNATIVE TO THE EM ALGORITHM FOR MAXIMIZING LIKELIHOODS IN EMISSION TOMOGRAPHY Author(s): BROWNE J; DEPIERRO AR Corporate Source: ARACOR,425 LAKESIDE DR/SUNNYVALE//CA/94086; STATE UNIV CAMPINAS,DEPT APPL MATH/BR-13081970 CAMPINAS//BRAZIL/ Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1996, V15, N5 (OCT), P 687-699 ISSN: 0278-0062 Language: ENGLISH Document Type: ARTICLE Abstract: The maximum likelihood (ML) approach to estimating the radioactive distribution in the body cross section has become very popular among researchers in emission computed tomography (ECT) since it has been shown to provide very good images compared to those produced with the conventional filtered backprojection (FBP) algorithm. The expectation maximization (EM) algorithm is an often-used iterative approach for maximizing the Poisson likelihood in ECT because of its attractive theoretical and practical properties. Its major disadvantage is that, due to its slow rate of convergence, a large amount of computation is often required to achieve an acceptable image. In this paper we present a row-action maximum likelihood algorithm (RAMLA) as an alternative to the EM algorithm for maximizing the Poisson likelihood in ECT. We deduce the convergence properties of this algorithm and demonstrate by way of computer simulations that the early iterates of RAMLA increase the Poisson likelihood in ECT at an order of magnitude faster that the standard EM algorithm. Specifically, we show that, from the point of view of measuring total radionuclide uptake in simulated brain phantoms, iterations 1, 2, 3, and 4 of RAMLA perform at least as well as iterations 45, 60, 70, and 80, respectively, of EM. Moreover, we show that iterations 1, 2, 3, and 4 of RAMLA achieve comparable likelihood values as iterations 45, 60, 70, and 80, respectively, of EM. We also present a modified version of a recent fast ordered subsets EM (OS-EM) algorithm and show that RAMLA is a special case of this modified OS-EM. Furthermore, we show that our modification converges to a ML solution whereas the standard OS-EM does not. 1/7/78 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 05111543 Genuine Article#: VA943 Number of References: 35 Title: IMPROVED SPECT QUANTITATION USING FULLY 3-DIMENSIONAL ITERATIVE SPATIALLY VARIANT SCATTER RESPONSE COMPENSATION Author(s): BEEKMAN FJ; KAMPHUIS C; VIERGEVER MA Corporate Source: UNIV UTRECHT HOSP,DEPT RADIOL & NUCL MED,ROOM E02222,HEIDELBERGLAAN 100/NL-3584 CX UTRECHT//NETHERLANDS/ Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1996, V15, N4 (AUG), P 491-499 ISSN: 0278-0062 Language: ENGLISH Document Type: ARTICLE Abstract: The quality and quantitative accuracy of iteratively reconstructed SPECT images improves when better point spread function (PSF) models of the gamma camera are used during reconstruction, In this paper, inclusion in the PSF model of photon crosstalk between different slices caused by limited gamma camera resolution and scatter is examined, A three-dimensional (3-D) projector back-projector (proback) has been developed which models both the distance dependent detector point spread function and the object shape-dependent scatter point spread function of single photon emission computed tomography (SPECT), A table occupying only a few megabytes of memory is sufficient to represent this scatter model, The contents of this table are obtained by evaluating an analytical expression for object shape-dependent scatter, The proposed approach avoids the huge memory requirements of storing the full transition matrix needed for 3-D reconstruction including object shape-dependent scatter. In addition, the method avoids the need for lengthy Monte Carlo simulations to generate such a matrix, In order to assess the quantitative accuracy of the method, reconstructions of a water filled cylinder containing regions of different activity levels and of simulated 3-D brain projection data have been evaluated for technetium-99m. It is shown that fully 3-D reconstruction including complete detector response and object shape-dependent scatter modeling clearly outperforms simpler methods that lack a complete detector response and/or a complete scatter response model, Fully 3-D scatter correction yields the best quantitation of volumes of interest and the best contrast-to-noise curves. 1/7/79 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 04923179 Genuine Article#: UT044 Number of References: 6 Title: SPATIAL HOMOGENEITY ISSUES WITH CONCURRENT ITERATIVE RECONSTRUCTION ALGORITHMS Author(s): TANG HR; BROWN JK; WU X; HASEGAWA BH Corporate Source: UNIV CALIF SAN FRANCISCO,DEPT RADIOL/SAN FRANCISCO//CA/94143; UNIV CALIF SAN FRANCISCO,BIOENGN GRAD GRP/SAN FRANCISCO//CA/94143; UNIV CALIF BERKELEY/BERKELEY//CA/94720 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1996, V43, N3 (JUN), P 2025-2029 ISSN: 0018-9499 Language: ENGLISH Document Type: ARTICLE Abstract: Concurrent Iterative Reconstruction Algorithms use projection data in the iterative process as the data become available during the SPECT acquisition process and continue iterations in the post-acquisition period as conventional iterative algorithms. Because projections acquired early are processed more than later projections, regional inhomogeneities may exist in the initial image estimates but decrease with further post-acquisition iteration. Regularization done either during the acquisition or post-acquisition iterations further reduces regional inhomogeneities. We tested statistical differences in regions throughout the reconstructed image to determine the minimal number of post-acquisition iterations and type of regularization needed to reach an image that is inter-regionally consistent. The algorithms provide images free of reconstruction inhomogeneities and can offer a reduction in post-acquisition reconstruction time when compared to conventional iterative algorithms. 1/7/80 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 04923178 Genuine Article#: UT044 Number of References: 18 Title: EVALUATION OF OS-EM VS ML-EM FOR 1D, 2D AND FULLY 3D SPECT RECONSTRUCTION Author(s): KAMPHUIS C; BEEKMAN FJ; VIERGEVER MA Corporate Source: UNIV UTRECHT HOSP,IMAGING CTR/UTRECHT//NETHERLANDS/ Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1996, V43, N3 (JUN), P 2018-2024 ISSN: 0018-9499 Language: ENGLISH Document Type: ARTICLE Abstract: For SPECT reconstruction, iterative Maximum Likelihood Expectation Maximization (ML-EM) estimation has a huge computational burden. The objective of this paper is to compare images obtained by ML-EM and an EM algorithm acting on Ordered Subsets of projections (OS-EM). Two digital phantoms, a cylinder with two cold spots and an ellipsoid with several hot spots and one cold spot were reconstructed from 120 simulated noisy projections. 1D (delta-like point source response), 2D (single slice response) and fully 3D reconstruction were investigated. Three quantities were calculated for the evaluation, viz. contrast, normalized standard deviation and mean squared error. In the case of fully 3D reconstruction, OS-EM 60 reconstructions (i.e., using 60 ordered subsets) were very close to ML-EM reconstructions. This shows that the OS-EM algorithm is an extremely fast and efficient method to accelerate iterative SPECT reconstruction with speed-up factors of close to half the number of projections. 1/7/81 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 04923175 Genuine Article#: UT044 Number of References: 27 Title: CALCULATION OF LUNG-HEART RATIOS FOR SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY Author(s): SOARES EJ; KING MA; GLICK SJ; VILLEGAS BJ Corporate Source: UNIV MASSACHUSETTS,MED CTR,DEPT NUCL MED/WORCESTER//MA/01655 Journal: IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 1996, V43, N3 (JUN), P 1995-1999 ISSN: 0018-9499 Language: ENGLISH Document Type: ARTICLE Abstract: We investigate the effectiveness of simple iterative reconstruction techniques in calculating lung-heart activity ratios (LHRs). The LHR has been shown to be an effective indicator of the severity of coronary artery disease in cardiac SPECT. A study was conducted with a mathematical cardiac torso phantom that modelled uptake of Tl-201 in the heart and lung regions. The projection data included only the effects of nonuniform photon attenuation The data were first reconstructed with zeroth-order Chang and a variant of the Bellini method, both of which utilize information from the nonuniform attenuation map. This nonuniform (NU) Bellini method compensates exactly for attenuation in the heart region, but is incorrect for other regions in the medium. These reconstructions were then used as the initial estimates in the iterative Chang, variable step-size (VSS) Chang, and Morozumi methods, for one and five iterations. The average heart count (AHC) and average lung count (ALC) were calculated using region-of-interest (ROI) templates derived from the true activity map. The population mean LHR was tabulated as the ratio of the ALC to AHC. Using the same reconstruction procedure, we also calculated the sample mean LHR and standard deviation from 21 noisy 3D reconstructions. The results showed that the NU Bellini and zeroth-order Chang methods provided good estimates of the AHC, while both estimated the ALC poorly. The NU Bellini method yielded a negative ALC, while the zeroth-order Chang method estimated the ALC at twice its true value. Application of one iteration of Chang can correct for the negative bias in the ALC for the NU Bellini estimate, and can correct for the positive bias in the ALC for the zeroth-order Chang estimate, while retaining a low bias in the AHCs for the two methods. Thus more precise LHRs are produced. Furthermore, the sample standard deviation of the LHR estimate was shown to be small in both of these cases. 1/7/82 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 04733065 Genuine Article#: UD860 Number of References: 38 Title: MEAN AND VARIANCE OF IMPLICITLY DEFINED BIASED-ESTIMATORS (SUCH AS PENALIZED MAXIMUM-LIKELIHOOD) - APPLICATIONS TO TOMOGRAPHY Author(s): FESSLER JA Corporate Source: UNIV MICHIGAN,DEPT ELECT ENGN & COMP SCI/ANN ARBOR//MI/48109; UNIV MICHIGAN,DEPT INTERNAL MED/ANN ARBOR//MI/48109 Journal: IEEE TRANSACTIONS ON IMAGE PROCESSING, 1996, V5, N3 (MAR), P 493-506 ISSN: 1057-7149 Language: ENGLISH Document Type: ARTICLE Abstract: Many estimators in signal processing problems are defined implicitly as the maximum of some objective function, Examples of implicitly defined estimators include maximum likelihood, penalized likelihood, maximum a posteriori, and nonlinear least squares estimation. For such estimators, exact analytical expressions for the mean and variance are usually unavailable, Therefore, investigators usually resort to numerical simulations to examine properties of the mean and variance of such estimators, This paper describes approximate expressions for the mean and variance of implicitly defined estimators of unconstrained continuous parameters, We derive the approximations using the implicit function theorem, the Taylor expansion, and the chain rule, The expressions are defined solely in terms of the partial derivatives of whatever objective function one uses for estimation, As illustrations, we demonstrate that the approximations work well in two tomographic imaging applications with Poisson statistics, We also describe a ''plug-in'' approximation that provides a remarkably accurate estimate of variability even from a single noisy Poisson sinogram measurement, The approximations should be useful in a wide range of estimation problems. 1/7/83 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 04608426 Genuine Article#: TW652 Number of References: 66 Title: ATTENUATION COMPENSATION FOR CARDIAC SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHIC IMAGING .2. ATTENUATION COMPENSATION ALGORITHMS Author(s): KING MA; TSUI BMW; PAN TS; GLICK SJ; SOARES EJ Corporate Source: UNIV MASSACHUSETTS,MED CTR,DEPT NUCL MED,55 LAKE AVE N/WORCESTER//MA/01655; UNIV N CAROLINA,DEPT BIOMED ENGN/CHAPEL HILL//NC/27515 Journal: JOURNAL OF NUCLEAR CARDIOLOGY, 1996, V3, N1 (JAN-FEB), P55-64 ISSN: 1071-3581 Language: ENGLISH Document Type: REVIEW Abstract: Attenuation is believed to be one of the major causes of false-positive cardiac single-photon emission computed tomographic perfusion images. This article provides an introduction to the approaches used to correct for nonuniform attenuation once a patient-specific attenuation map is available. Comparison is made of specific attenuation-correction algorithms from each of three major categories of compensation methods that are or will be available commercially, Examples of the use of the algorithms on simulated projections of a mathematic phantom modeling the anatomy of the upper torso are used to illustrate the ability of the methods to compensate for attenuation. The advantages and disadvantages of each approach are summarized, as well as areas that need further investigation. 1/7/84 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 04593738 Genuine Article#: TV746 Number of References: 42 Title: PRACTICAL CONSIDERATIONS FOR 3-D IMAGE-RECONSTRUCTION USING SPHERICALLY SYMMETRICAL VOLUME ELEMENTS Author(s): MATEJ S; LEWITT RM Corporate Source: UNIV PENN,DEPT RADIOL,MED IMAGE PROC GRP/PHILADELPHIA//PA/19104; SLOVAK ACAD SCI,INST MEASUREMENT SCI/BRATISLAVA//SLOVAKIA/ Journal: IEEE TRANSACTIONS ON MEDICAL IMAGING, 1996, V15, N1 (FEB), P68-78 ISSN: 0278-0062 Language: ENGLISH Document Type: ARTICLE Abstract: Spherically symmetric volume elements with smooth tapering of the values near their boundaries are alternatives to the more conventional voxels for the construction of volume images in the computer, Their use, instead of voxels, introduces additional parameters which enable the user to control the shape of the volume element (blob) and consequently to control the characteristics of the images produced by iterative methods for reconstruction from projection data, For images composed of blobs, efficient algorithms have been designed for the projection and discrete back-projection operations, which are the crucial parts of iterative reconstruction methods, We have investigated the relationship between the values of the blob parameters and the properties of images represented by the blobs, Experiments show that using blobs in iterative reconstruction methods leads to substantial improvement in the reconstruction performance, based on visual quality and on quantitative measures, in comparison with the voxel case. The images reconstructed using appropriately chosen blobs are characterized by less image noise for both noiseless data and noisy data, without loss of image resolution. 1/7/85 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 04368461 Genuine Article#: RY664 Number of References: 53 Title: PENALIZED MAXIMUM-LIKELIHOOD IMAGE-RECONSTRUCTION USING SPACE-ALTERNATING GENERALIZED EM ALGORITHMS Author(s): FESSLER JA; HERO AO Corporate Source: UNIV MICHIGAN,DEPT ELECT ENGN & COMP SCI/ANN ARBOR//MI/48109 Journal: IEEE TRANSACTIONS ON IMAGE PROCESSING, 1995, V4, N10 (OCT), P 1417-1429 ISSN: 1057-7149 Language: ENGLISH Document Type: ARTICLE Abstract: Most expectation-maximization (EM) type algorithms for penalized maximum-likelihood image reconstruction converge slowly, particularly when one incorporates additive background effects such as scatter, random coincidences, dark current, or cosmic radiation, In addition, regularizing smoothness penalties (or priors) introduce parameter coupling, rendering intractable the M-steps of most EM-type algorithms, This paper presents space-alternating generalized EM (SAGE) algorithms for image reconstruction, which update the parameters sequentially using a sequence of small ''hidden'' data spaces, rather than simultaneously using one large complete-data space, The sequential update decouples the M-step, so the maximization can typically be performed analytically, We introduce new hidden-data spaces that are less informative than the conventional complete-data space for Poisson data and that yield significant improvements in convergence rate, This acceleration is due to statistical considerations, not numerical overrelaxation methods, so monotonic increases in the objective function are guaranteed, We provide a general global convergence proof for SAGE methods with nonnegativity constraints. 1/7/86 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 04283834 Genuine Article#: RU095 Number of References: 29 Title: SIMULTANEOUS EMISSION AND TRANSMISSION MEASUREMENTS FOR ATTENUATION CORRECTION IN WHOLE-BODY PET Author(s): MEIKLE SR; BAILEY DL; HOOPER PK; EBERL S; HUTTON BF; JONES WF Corporate Source: ROYAL PRINCE ALFRED HOSP,DEPT PET,MISSENDEN RD/CAMPERDOWN/NSW 2050/AUSTRALIA/; ROYAL PRINCE ALFRED HOSP,DEPT PET,DIV MED IMAGING SERV/SYDNEY/NSW/AUSTRALIA/; CTI PET SYST/KNOXVILLE//TN/00000 Journal: JOURNAL OF NUCLEAR MEDICINE, 1995, V36, N9 (SEP), P1680-1688 ISSN: 0161-5505 Language: ENGLISH Document Type: ARTICLE Abstract: We describe a methodology for measuring and correcting for attenuation in whole-body PET using simultaneous emission and transmission (SET) measurements. Methods: The main components of the methodology are: (a) sinogram windowing of low activity (less than or equal to 50 MBq) rotating Ge-68/Ga rod sources, (b) segmented attenuation correction (SAC) and (c) maximum likelihood reconstruction using the ordered subsets EM (OS-EM) algorithm. The methods were implemented on a whole-body positron emission tomograph. Quantitative accuracy and the signal-to-noise ratio (SNR) were measured for a thorax-tumor phantom as functions of acquisition time (range: 2-20 min per position). Results: When a typical rod source activity (200 MBq Ge-68/Ga) was used, emission SNR was 60% lower in simultaneous than in separate measurements. The difference was only 14% when the rods contained 45 MBq Ge-68/Ga. The SNR was further improved by SAC in conjunction with OS-EM reconstruction and the relative gain increased with increasing acquisition time. Quantitative estimates of tumor, liver and lung radioactivity agreed with values obtained from a separate high count measurement to within 8%, independent of acquisition time. Conclusion: Attenuation correction of whole-body PET images is feasible using SET measurements. There is good quantitative agreement with conventional methods and increased noise is offset by the use of SAC and OS-EM reconstruction. 1/7/87 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 04143714 Genuine Article#: RH556 Number of References: 30 Title: TRANSMISSION MAXIMUM-LIKELIHOOD RECONSTRUCTION WITH ORDERED SUBSETS FOR CONE-BEAM CT Author(s): MANGLOS SH; GAGNE GM; KROL A; THOMAS FD; NARAYANASWAMY R Corporate Source: SUNY HLTH SCI CTR,DEPT RADIOL,750 E ADAMS ST/SYRACUSE//NY/13210; TRIONIX RES LAB INC/TWINSBURG//OH/44087 Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1995, V40, N7 (JUL), P1225-1241 ISSN: 0031-9155 Language: ENGLISH Document Type: ARTICLE Abstract: An iterative algorithm is presented for accelerated reconstruction of cone beam transmission CT data (CBCT). CBCT supplies an attenuation map for SPECT attenuation compensation and anatomical correlation. Iterative algorithms are necessary to reduce truncation artifacts and 3D reconstruction artifacts. An existing transmission maximum-likelihood algorithm (TRML) is accurate but the reconstruction time is too long. The new algorithm is a modified EM algorithm, based on ordered subsets (OSEM). OSEM was evaluated in comparison to TRML using a thorax phantom and a 3D Defrise phantom. A wide range of image measures were evaluated, including spatial resolution, noise, log likelihood, region quantification, truncation artifact removal, and 3D artifact removal. For appropriate subset size, OSEM produced essentially the same image as TRML, but required only one-tenth as many iterations. Thus, adequate images were available in two to four iterations (20-30 min on a SPARC 2 workstation). Further, OSEM still approximately maximizes likelihood: divergence occurs only for very high (and clinically irrelevant) iterations. Ordered subsets are likely to be useful in other geometries (fan and parallel) and for emission CT as well. Therefore, with ordered subsets, high-quality iterative reconstruction is now available in clinically practical reconstructions times. 1/7/88 DIALOG(R)File 34:SciSearch(R) Cited Ref Sci (c) 1998 Inst for Sci Info. All rts. reserv. 03537990 Genuine Article#: PK957 Number of References: 24 Title: ACCELERATED EM RECONSTRUCTION IN TOTAL-BODY PET - POTENTIAL FOR IMPROVING TUMOR DETECTABILITY Author(s): MEIKLE SR; HUTTON BF; BAILEY DL; HOOPER PK; FULHAM MJ Corporate Source: ROYAL PRINCE ALFRED HOSP,DEPT NUCL MED,MISSENDEN RD/CAMPERDOWN 2050/NSW/AUSTRALIA/ Journal: PHYSICS IN MEDICINE AND BIOLOGY, 1994, V39, N10 (OCT), P1689-1704 ISSN: 0031-9155 Language: ENGLISH Document Type: ARTICLE Abstract: Total-body positron emission tomography (PET) is a useful diagnostic tool for evaluating malignant disease. However, tumour detection is limited by image artefacts due to the lack of attenuation correction and noise. Attenuation correction may be possible using transmission data acquired after or simultaneously with emission data. Despite the elimination of attenuation artefacts, however, tumour detection is still hampered by noise, which is amplified during image reconstruction by filtered backprojection (FBP). We have investigated, as an alternative to FBP, an accelerated expectation maximization (EM) algorithm for its potential to improve tumour detectability in total-body PET. Signal to noise ratio (SNR), calculated for a tumour with respect to the surrounding background, is used as a figure of merit. A software tumour phantom, with conditions typical of those encountered in a total-body PET study using simultaneous acquisition, is used to optimize and compare various reconstruction approaches. Accelerated EM reconstruction followed by two-dimensional filtering is shown to yield significantly higher SNR than FBP for a range of tumour sizes, concentrations and counting statistics (Delta SNR = 6.3 +/- 3.9, p < 0.001). The methods developed are illustrated by examples derived from physical phantom and patient data. Di van Sommers Academic Outreach Librarian - Science and Technology Macquarie University Library Macquarie University Australia phone:61 2 9850 7892 email: dvansomm@library.mq.edu.au fax: 61 2 9850 7513