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Nuclear Science, IEEE Transactions on

Issue 3  Part 2 • Date June 1997

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Displaying Results 1 - 25 of 51
  • Conference Author Index

    Publication Year: 1997 , Page(s): 1420 - 1421
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    Freely Available from IEEE
  • A data acquisition system for coincidence imaging using a conventional dual head gamma camera

    Publication Year: 1997 , Page(s): 1214 - 1218
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    A low cost data acquisition system (DAS) was developed to acquire coincidence data from an unmodified General Electric Maxxus dual head scintillation camera. A high impedance pick-off circuit provides position and energy signals to the DAS without interfering with normal camera operation. The signals are pulse-clipped to reduce pileup effects. Coincidence is determined with fast timing signals derived from constant fraction discriminators. A charge-integrating FERA 16 channel ADC feeds position and energy data to two CAMAC FERA memories operated as ping-pong buffers. A Macintosh PowerPC running Labview controls the system and reads the CAMAC memories. A CAMAC 12-channel scaler records singles and coincidence rate data. The system dead-time is approximately 10% at a coincidence rate of 4.0 kHz View full abstract»

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  • Region of interest evaluation of SPECT image reconstruction methods using a realistic brain phantom

    Publication Year: 1997 , Page(s): 1336 - 1341
    Cited by:  Papers (1)
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    A realistic numerical brain phantom, developed by Zubal et al. (1994), 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 View full abstract»

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  • A count rate model for PET and its application to an LSO HR PLUS scanner

    Publication Year: 1997 , Page(s): 1219 - 1224
    Cited by:  Papers (15)
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    Considering a standard 20×20 cm phantom in the field-of-view of a cylindrical, septaless tomograph, the count rate model computes the acceptance to prompt and random events from simple geometric considerations. Dead time factors at all stages of a typical event acquisition architecture are calculated from specified processing clock cycles. Validations of the model's predictions against the measured performances of the ECAT-953B and the EXACT HR PLUS are presented. The model is then used to investigate the benefit of using detectors made of LSO in the EXACT HR PLUS scanner geometry. The results indicate that in replacing BGO by the faster LSO, one can count on an increase of the peak noise-equivalent-count rate by a factor 2.2. This gain will be achieved by using a 5 nsec coincidence window, buckets operating on a 128 nsec clock cycle, and a front-end data acquisition that can sustain a total event rate of 2.9 MHz View full abstract»

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  • Attenuation correction strategies for multi-energy photon emitters using SPECT

    Publication Year: 1997 , Page(s): 1323 - 1328
    Cited by:  Papers (11)
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    The aim of this study was 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 over-estimation with strategy 1, an under-estimation with strategy 2 and comparable results with strategies 3 and 4. In all strategies, the CCRs of sphere 4 (in proximity to the liver, spleen and backbone) were under-estimated, although TCRs 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 View full abstract»

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  • Investigation of LSO crystals for high spatial resolution positron emission tomography

    Publication Year: 1997 , Page(s): 1109 - 1113
    Cited by:  Papers (55)  |  Patents (2)
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    In order to achieve high sensitivity and maintain good uniform spatial. Resolution over the field of view in high resolution PET systems, adequate depth of interaction information must be extracted from the crystal. A phoswich detector can supply one solution to the depth of interaction problem. In this approach, two or more scintillators exhibiting different light decay times are positioned on top of each other and separated by pulse shape discrimination. Initially, the authors' experiments focused on separating different types of scintillators such as LSO and GSO or LSO and YSO. These combinations were all well separated as expected. During the investigation, a shift in the time distribution of different samples of LSO was noticed. Further investigation showed two groups of LSO. The shift in the zero cross time was more than twice the FWHM of the time distribution. A single photon experiment revealed that the decay time of the `fast' crystal was 33.4 nanoseconds while the decay of the `slow' crystal was 42.2 nanoseconds. A spectral plot revealed that the spectral output of the `slow' crystal was skewed to the longer wavelengths as compared to the `fast' crystal. Further investigation on other crystal samples revealed decay times between the two extremes, suggesting a continuum in the light decay View full abstract»

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  • Estimation of scattered photons in gamma ray transmission CT using Monte Carlo simulations

    Publication Year: 1997 , Page(s): 1225 - 1230
    Cited by:  Papers (6)
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    Quantitative image reconstruction in single photon emission CT requires an accurate attenuation map of a cross section of an object. Several data acquisition geometries have been proposed to obtain the true attenuation map by means of gamma-ray transmission CT (TCT). In the transmission data scattered photons are sometimes measured and they reduce the accuracy of reconstructed TCT images. To investigate the effects of scattered photons in gamma-ray transmission CT, we performed Monte Carlo simulations for several types of data acquisition systems. Examined geometries were (a) an uncollimated flood source and a parallel hole collimator, (b) a collimated flood source and a parallel hole collimator, (c) an uncollimated line source and a symmetric fan beam collimator, and (d) a collimated line source and a symmetric fan beam collimator. The results showed that a fan beam collimator and a line source rejected most of the scattered photons generated inside an object, and that if we collimated emitted photons at the source side, almost all the scattered photons could be rejected at the collimator on the detector side View full abstract»

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  • Bone equivalent liquid solution to assess accuracy of transmission measurements in SPECT and PET

    Publication Year: 1997 , Page(s): 1186 - 1190
    Cited by:  Papers (5)  |  Patents (1)
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    Quantitation in Emission Tomography (PET and SPECT) requires that several physical factors are taken into account. Attenuation, which can be determined on SPECT and PET devices, can be corrected using transmission tomography. Here, the authors quantitatively compared the relative performance of transmission scans in SPECT and PET using a calibrated liquid solution with a linear attenuation coefficient (μ) nearly equivalent to that of skeletal cranium bone over the range of energies 50 to 600 keV. The authors showed that contrast recovery are similar in PET and SPECT for large structures (>30 mm), but higher in PET as object size decreases View full abstract»

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  • Automated region selection for analysis of dynamic cardiac SPECT data

    Publication Year: 1997 , Page(s): 1355 - 1361
    Cited by:  Papers (10)  |  Patents (1)
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    Dynamic cardiac SPECT using Tc-99m labeled teboroxime can provide kinetic parameters (washin, washout) indicative of myocardial blood flow. A time-consuming and subjective step of the data analysis is drawing regions of interest to delineate blood pool and myocardial tissue regions. The time-activity curves of the regions are then used to estimate local kinetic parameters. In this work, the appropriate regions are found automatically, in a manner similar to that used for calculating maximum count circumferential profiles in conventional static cardiac studies. The drawbacks to applying standard static circumferential profile methods are the high noise level and high liver uptake common in dynamic teboroxime studies. Searching along each ray for maxima to locate the myocardium does not typically provide useful information. Here we propose an iterative scheme in which constraints are imposed on the radii searched along each ray. The constraints are based on the shape of the time-activity curves of the circumferential profile members and on an assumption that the short axis slices are approximately circular. The constraints eliminate outliers and help to reduce the effects of noise and liver activity. Kinetic parameter estimates from the automatically generated regions were comparable to estimates from manually selected regions in dynamic canine teboroxime studies View full abstract»

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  • Development of a PET detector system compatible with MRI/NMR systems

    Publication Year: 1997 , Page(s): 1167 - 1171
    Cited by:  Papers (59)  |  Patents (6)
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    We report the development of a prototype positron emission tomography (PET) scanner compatible with clinical magnetic resonance imaging (MRI) scanners and nuclear magnetic resonance (NMR) spectrometers. This single slice PET system consists of 72 2×2×5 mm lutetium oxyorthosilicate (LSO) crystals coupled by 2 mm diameter, 4 meter long double clad optical fibers to three multi-channel photomultiplier tubes (MC-PMTs) shielded inside an aluminum closure. The ring diameter is 54 mm and the slice thickness is ~1 mm FWHM. Measurements with a point source demonstrate that this PET system has a reconstructed resolution of 2.1 mm, a coincidence time resolution of 26 ns and a typical energy resolution of 45%. Simultaneously acquired PET and MR phantom images, show no significant artifacts or distortions. We also obtained simultaneous NMR spectra and PET images from an isolated, perfused rat heart, demonstrating the power of obtaining temporally correlated PET and NMR information in biological systems. Again, no artifacts in the PET or NMR data were apparent, despite the high field strength of 9.4 T. The challenge for the future is to scale up the design to develop a high resolution, high sensitivity device that can be used in simultaneous PET and MR studies of in vivo systems View full abstract»

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  • Energy-subtraction Compton scatter camera design considerations: a Monte Carlo study of timing and energy resolution effects

    Publication Year: 1997 , Page(s): 1134 - 1139
    Cited by:  Papers (6)  |  Patents (1)
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    An energy-subtraction Compton scatter camera (ESCSC) was previously proposed for medical imaging applications. This ESCSC consists of a primary detector system (silicon) and a secondary detector system (cadmium-zinc-telluride) for preferred detection of Compton scatter and photoelectric absorption interactions, respectively. To further evaluate the usefulness of this ESCSC for medical imaging, the following characteristics have been simulated: the random emission of gamma-rays in time; detector timing, energy and spatial resolution; list mode data acquisition; and post-acquisition coincidence analysis. The resulting optimization of detector characteristics, data acquisition and analysis techniques, and administered activity is presented and discussed. One significant result of these simulations is that a localized activity of about 1.0 mCi allows for recovery of the majority of preferred events while eliminating the majority of interfering events when 10 and 50 ns FWHM timing resolutions for silicon and cadmium-zinc-telluride, respectively, are assumed. Consequently, the Proposed ESCSC should be capable of acquiring data for administered activities similar to those used with current mechanically-collimated imaging cameras View full abstract»

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  • Prone breast tumor imaging using vertical axis-of-rotation (VAOR) SPECT systems: an initial study

    Publication Year: 1997 , Page(s): 1271 - 1276
    Cited by:  Papers (24)  |  Patents (1)
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    The authors propose the use of a single photon emission computed tomography (SPECT) system equipped with multiple cameras which revolve around a vertical axis-of-rotation (VAOR) for prone-dependent (i.e., patient in prone position) breast tumor imaging. This geometry for nuclear medicine breast imaging reduces the amount of attenuating material between the breast tissue and the gamma camera and, in addition, it offers a minimal radius-of-rotation compared to breast imaging using conventional (i.e., 360°, horizontal axis-of-rotation) SPECT. The decrease in attenuation and radius-of-rotation results in an increase in detected counts and increased collimator resolution. Because VAOR SPECT systems are currently not commercially available, the authors conducted their experiments on a conventional SPECT system using an isolated breast phantom to investigate the proposed VAOR method. The authors' experimental setup simulated a VAOR SPECT study with a prone-dependent breast in the camera's field-of-view. The results of the experiment indicate that VAOR breast SPECT with Trionix low-energy super-high resolution (LESR) parallel-hole collimation is capable of detecting a breast lesion with an outer diameter of 10 mm and a lesion-to-background concentration ratio of 6-to-1. The results also demonstrate that VAOR breast SPECT provides improved lesion parallel-hole planar imaging (i.e., scintimammography) and breast imaging using horizontal axis-of-rotation SPECT View full abstract»

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  • Discrete scintillator coupled mercuric iodide photodetector arrays for breast imaging

    Publication Year: 1997 , Page(s): 1127 - 1133
    Cited by:  Papers (10)
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    Multi-element (4×4) imaging arrays with high resolution collimators, size matched to discrete CsI(Tl) scintillator arrays and mercuric iodide photodetector arrays (HgI2 PDA) were developed as prototypes for larger 16×16 element arrays for breast imaging. The compact nature of the arrays allows detector positioning in close proximity to the breast to eliminate activity not in the line-of-sight of the collimator, thus reducing image background. Short collimators, size matched to 11.5×1.5 mm2 scintillators show a factor of 2 and 3.4 improvement in spatial resolution and efficiency, respectively, compared to high resolution collimated gamma cameras for the anticipated compressed breast geometries. Monte Carlo simulations, confirmed by measurements, demonstrated that scintillator length played a greater role in efficiency and photofraction for 140 keV gammas than cross sectional area, which affects intrinsic spatial resolution. Simulations also demonstrated that an increase in the ratio of scintillator area to length corresponds to an improvement in light collection. Electronic noise was below 40 e- RMS indicating that detector resolution was not noise limited. The high quantum efficiency and spectral match of prototype unity gain HgI2 PDAs coupled to 1×1×2.5 mm3 and 2×2×4 mm3 CsI(Tl) scintillators demonstrated energy resolutions of 9.4% and 8.8% FWHM at 140 keV, respectively, without the spectral tailing observed in standard high-Z, compound semiconductor detectors. Line spread function measurements matched the scintillator size and pitch, and small, complex phantoms were easily imaged View full abstract»

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  • MicroPET: a high resolution PET scanner for imaging small animals

    Publication Year: 1997 , Page(s): 1161 - 1166
    Cited by:  Papers (239)  |  Patents (8)
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    MicroPET is a high resolution positron emission tomography (PET) scanner designed for imaging small laboratory animals. It consists of a ring of 30 position-sensitive scintillation detectors, each with an 8×8 array of small lutetium oxyorthosilicate (LSO) crystals coupled via optical fibers to a multi-channel photomultiplier tube. The detectors have an intrinsic resolution averaging 1.68 mm, an energy resolution between 15 and 25% and 2.4 ns timing resolution at 511 keV. The detector ring diameter of microPET is 17.2 cm with an imaging field of view of 112 mm transaxially by 18 mm axially. The scanner has no septa and operates exclusively in 3D mode. Reconstructed image resolution 1 cm from the center of the scanner is 2.0 mm and virtually isotropic, yielding a volume resolution of 8 mm3. For comparison, the volume resolution of state-of-the-art clinical PET systems is in the range of 50-75 mm3. Initial images of phantoms have been acquired and are reported. A computer controlled bed is under construction and will incorporate a small wobble motion to improve spatial sampling. This is projected to further enhance spatial resolution. MicroPET is the first PET scanner to incorporate the new scintillator LSO and to our knowledge is the highest resolution multi-ring PET scanner currently in existence View full abstract»

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  • Reconstruction and visualization of 3D models of colonic surface

    Publication Year: 1997 , Page(s): 1297 - 1302
    Cited by:  Papers (18)  |  Patents (3)
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    Presents an innovative technology called 3D virtual colonoscopy, which incorporates several advanced visualization techniques to enable the physician to virtually examine the inner surface of the entire colon for identifying and inspecting colonic polyps. The authors first describe their unique process of acquiring and reconstructing a patient's colon model, followed by the novel visualization algorithms that they have developed to provide automatic planned navigations as well as interactive guided navigations inside the colon. Finally, the authors present their experimental results on a simulated pipe phantom, the Visible Human data set, and patient data View full abstract»

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  • Small lesion visualization in scintimammography

    Publication Year: 1997 , Page(s): 1398 - 1402
    Cited by:  Papers (7)
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    For scintimammography (SMM) to have wide clinical use, physicians must be able to rapidly direct biopsy of small cancers. The authors therefore undertook a theoretical and experimental study of lesion visibility vs. acquisition time and tumor size. Theoretical considerations as to acquisition time and contrast suggested that compression would significantly improve lesion visibility for small cancers. These predictions were confirmed with phantom studies. Patient studies showed that high confidence images of small primary breast tumors can be produced with the addition of breast compression. The authors conclude that breast compression would improve SMM detection of small primary breast cancers View full abstract»

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  • Investigations into possible causes of hot inferior wall artifacts in attenuation corrected cardiac perfusion images

    Publication Year: 1997 , Page(s): 1146 - 1153
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    Through our investigations with simulated images, we have identified several causes of hot inferior wall artifacts in attenuation corrected SPECT cardiac perfusion images. With an insufficient number of iterations, the non-uniform resolution recovered in three dimensions and slow convergence rate of ML-EM reconstruction can cause this artifact when the heart is at a shallow angle (the axis of the heart is close to being horizontal) or when there exists significant background activity. Increasing the number of iterations does not correct this artifact when the attenuation map used has poor resolution or its attenuation coefficients used are not accurate. We also notice that the hot inferior wall artifact is more pronounced when body contouring acquisition or 180° angular sampling is used View full abstract»

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  • Investigation of a new readout scheme for high resolution scintillation crystal arrays using photodiodes

    Publication Year: 1997 , Page(s): 1208 - 1213
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    We are exploring the possibility of using PIN photodiodes to readout the scintillation crystals used in positron emission tomography (PET) detector designs. Semiconductor photodetectors typically have a lower signal to noise ratio than photomultiplier tubes (PMTs). However, they have the advantage of compactness, and, thus, scintillation crystal readout schemes not available to PMTs because of their size and geometry limitations, are readily available to photodiodes. With current PET detector designs, only a small fraction of the available scintillation light, created from 511 keV gamma ray interactions within the crystal, is collected. Scintillation light collection studies were performed for several crystal geometries and surface treatments using both simulations and measurements. In this report, we present a feasible photodiode readout scheme that allows greater than 90% of the available scintillation light created in either BGO or LSO scintillation crystals to be collected by the photodetector. This improvement in light collection with the photodiode readout somewhat compensates for its lower inherent signal to noise ratios and makes it feasible for use in PET detectors. A coincident timing spectrum resolution of 9.4 ns FWHM was measured for 511 keV interactions with one LSO crystal coupled to a photodiode, the other to a PMT View full abstract»

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  • Fast iterative segmentation of high resolution medical images

    Publication Year: 1997 , Page(s): 1362 - 1367
    Cited by:  Papers (5)
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    Various applications in positron emission tomography (PET), single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) require segmentation of 20 to 60 high resolution images of size 256×256 pixels in 3-9 seconds per image. This places particular constraints on the design of image segmentation algorithms. This paper proposes a quantized data representation and a quantised EM algorithm for estimating the parameters of a finite mixture density function to be used in a Bayes classifier for image segmentation. Both a Monte Carlo evaluation and an application to MRI images showed that the quantized EM algorithm can dramatically reduce the required computation time with negligible difference in mean estimation error and mean classification error View full abstract»

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  • Performance evaluation of the whole-body PET scanner ECAT EXACT HR + following the IEC standard

    Publication Year: 1997 , Page(s): 1172 - 1179
    Cited by:  Papers (79)
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    The performance parameters of the whole-body PET scanner ECAT EXACT HR+ (CTI/Siemens, Knoxville, TN) were determined following the standard proposed by the International Electrotechnical Commission (IEC). The tests were expanded by some measurements concerning the accuracy of the correction algorithms and the geometric fidelity of the reconstructed images. The scanner consists of 32 rings, each with 576 BGO detectors (4.05×4.39×30 mm3), covering an axial field-of-view of 15.5 cm and a patient port of 56.2 cm. The transaxial FWHM determined by a Gaussian fit in the 2D (3D) mode is 4.5 (4.3) mm at the center. It increases to 8.9 (8.3) mm radially and to 5.8 (5.2) mm tangentially at a radial distance of r=20 cm. The average axial resolution varies between 4.9 (4.1) mm FWHM at the center and 8.8 (8.1) mm at r=20 cm. The system sensitivity for unscattered true events is 5.85 (26.4) cps/Bq/ml (measured with a 20 cm cylinder). The 50% dead-time losses were reached for a true event count rate (including scatter) of 286 (500) kcps at an activity concentration of 74 (25) kBq/ml. The system scatter fraction is 0.24 (0.35). With the exception of the 3D attenuation correction algorithm, all correction algorithms work reliably. The results reveal that the ECAT EXACT HR+ has a good and nearly isotropic spatial resolution. Due to the small detector elements, however, it has a low slice sensitivity which is a limiting factor for image quality View full abstract»

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  • The effect of heart motion on kinetic parameter estimates for dynamic cardiac SPECT

    Publication Year: 1997 , Page(s): 1409 - 1416
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (976 KB)  

    Dynamic cardiac SPECT is used to estimate kinetic rate parameters that describe the washin and washout of tracer activity between the blood and the myocardial tissue. These kinetic parameters correlate to myocardial perfusion. There are, however, many physical aspects associated with dynamic SPECT which introduce bias and variance into the estimates. This paper describes a study which investigates the effect of heart motion on kinetic parameter estimates. Dynamic SPECT simulations are performed using a beating version of the MCAT phantom. The amount of blood and background activity in the myocardial tissue regions of interest is shown to vary over the cardiac cycle causing errors in the kinetic parameter estimates, particularly estimates of the washin rate constant. The effect of cardiac motion on kinetic parameter estimates is reduced by bias and variance introduced by photon noise and geometric collimator response. This suggests that techniques used to correct for motion must do so without further reducing photon statistics View full abstract»

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  • Characterization of a 64 channel PET detector using photodiodes for crystal identification

    Publication Year: 1997 , Page(s): 1197 - 1201
    Cited by:  Papers (22)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    The authors present performance results for a prototype PET detector module consisting of 64 LSO scintillator crystals (3×3×20 mm) coupled on one end to a single photomultiplier tube and on the opposite end to a 64 pixel array of 3 mm square silicon photodiodes (typical pixel parameters are 5 pF capacitance, 300 pA dark current, and 73% quantum efficiency at 415 nm). The photomultiplier tube (PMT) provides an accurate timing pulse and energy threshold for all crystals in the module, the silicon photodiodes (PD) identify the crystal of interaction, the sum (PD+PMT) provides a total energy signal, and the PD/(PD+PMT) ratio determines the depth of interaction. With 32 of the channels instrumented, the detector module correctly identifies the crystal of interaction (where “correct” includes the adjacent 4 crystals) 79±4% of the time with high detection efficiency. The timing resolution for a single LSO detector module is 750 ps fwhm, while its pulse height resolution at 511 keV is 24±3% fwhm. The depth of interaction measurement resolution is 8±1 mm fwhm View full abstract»

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  • Evaluation of 3D reconstruction algorithms for a small animal PET camera

    Publication Year: 1997 , Page(s): 1303 - 1308
    Cited by:  Papers (38)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    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. The authors 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 18 F-fluoride suggest that 3D EM and 3D OSEM can improve image quality of a small animal PET camera View full abstract»

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  • Non-iterative methods and their noise characteristics in 2D SPECT image reconstruction

    Publication Year: 1997 , Page(s): 1388 - 1397
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1212 KB)  

    The authors derive explicit relationships between an ideal sinogram in 2D SPECT and the sinogram after degradation by constant attenuation and by distance-dependent spatial resolution that is described by either a Cauchy or a Gaussian function. Attempts to reduce statistical variance in the reconstructed image lead to the development of infinite classes of closed-form methods for estimation of the ideal sinogram. The authors applied this approach to 2D SPECT in both computer-simulation and real-data studies. Extensive computer-simulation studies demonstrate that the counterparts of a “quasi-optimal” method, which the authors had proved to be the optimal member of its class in 2D SPECT when only attenuation is present, provide the smallest global image variance among the methods in their classes also when Cauchy or Gaussian functions describe the distance-dependent spatial resolution function View full abstract»

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  • Analytical reconstruction formula for one-dimensional Compton camera

    Publication Year: 1997 , Page(s): 1342 - 1346
    Cited by:  Papers (13)  |  Patents (1)
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    The Compton camera has been proposed as an alternative to the Anger camera in SPECT. The advantage of the Compton camera is its high geometric efficiency due to electronic collimation. The Compton camera collects projections that are integrals over cone surfaces. Although some progress has been made toward image reconstruction from cone projections, at present no filtered backprojection algorithm exists. This paper investigates a simple 2D version of the imaging problem. An analytical formula is developed for 2D reconstruction from data acquired by a 1D Compton camera that consists of two linear detectors; one behind the other. Coincidence photon detection allows the localization of the 2D source distribution to two lines in the shape of a “V” with the vertex on the front detector. A set of “V” projection data can be divided into subsets whose elements can be viewed as line-integrals of the original image added with its mirrored shear transformation. If the detector has infinite extent, reconstruction of the original image is possible using data from only one such subset. Computer-simulations were performed to verify the newly developed algorithm View full abstract»

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IEEE Transactions on Nuclear Science focuses on all aspects of the theory and applications of nuclear science and engineering, including instrumentation for the detection and measurement of ionizing radiation; particle accelerators and their controls; nuclear medicine and its application; effects of radiation on materials, components, and systems; reactor instrumentation and controls; and measurement of radiation in space.

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