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Nuclear Science, IEEE Transactions on

Issue 3  Part 1 • Date June 2005

 This issue contains several parts.Go to:  Part 2 

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Displaying Results 1 - 25 of 26
  • [Front cover]

    Publication Year: 2005 , Page(s): c1
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  • IEEE Transactions on Nuclear Science publication information

    Publication Year: 2005 , Page(s): c2
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  • Table of contents

    Publication Year: 2005 , Page(s): 553 - 554
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  • Sampling considerations for high resolution small animal SPECT

    Publication Year: 2005 , Page(s): 555 - 559
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB) |  | HTML iconHTML  

    Using the small animal hybrid PET/SPECT scanner YAP-(S)PET we demonstrate how we can improve both image quality and spatial resolution in SPECT modality, by acquiring data with sampling steps smaller than the detector intrinsic sampling pitch. Due to the planar configuration of our pixellated detector we can easily perform this by shifting detector heads from the central position of an arbitrarily small step tangential to the field of view. This acquisition technique, together with the knowledge of the detector response function, allows us to determine the best sampling step as a trade-off between image quality, resolution, and acquisition time. In the real case, the more one samples the FOV with a finer step, the more one reduces aliasing (better image quality). Furthermore one also records higher frequency components in the image spectrum (better spatial resolution). To demonstrate how this technique can enhance the image, images of capillaries and phantoms will be presented. In particular the trend of resolution versus sampling step is reported. In this paper we present two different kinds of results: first we reconstruct images, acquired with different sampling modalities, with the same spatial frequency cut-off; in this way we show how the decreasing of the sampling step enhances image quality for a fixed resolution. Second we reconstruct images by recovering all possible spatial frequencies so as to enhance spatial resolution. All images are deconvolved for the frequency response (transfer function) of our system by implementing deconvolution in a standard filtered back projection (FBP) algorithm. The results show that it is possible to approach the 2 mm resolution limit imposed by the crystal; in fact we can recover resolution down to 2.2 mm (±3.5%). View full abstract»

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  • Depth of γ-ray interaction within continuous crystals from the width of its scintillation light-distribution

    Publication Year: 2005 , Page(s): 560 - 572
    Cited by:  Papers (48)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB) |  | HTML iconHTML  

    We have studied a new and inexpensive method of measuring the depth of interaction (DOI) in γ-ray detectors with large-sized scintillation crystals. This method takes advantage of the strong correlation between the width of the undisturbed light-distribution in continuous crystals and the γ-ray's DOI. In order to quantify the dependence of the distribution's width with respect to the DOI, we first studied an analytical model of the light-distribution and tested it by means of Monte Carlo (MC) simulations of the light transport inside the crystal. Further we present an inexpensive modification of the commonly used charge division circuit that allows analog and instantaneous computation of the light-distribution's second moment without affecting the determination of the centroid. This redesigned resistor network is based on the position-sensitive proportional counter (DPC) readout and allows, together with position sensitive photo-detectors, the additional measurement of the light-distribution's standard-deviation σ. We tested the proposed circuit using the design-tool OrCAD and found the signal sufficiently large for digitalization. Finally, we conducted MC simulations of a realistic Positron Emission Tomography (PET) detector module setup that mimic a continuous Lu2SiO5:Ce3+ (LSO) crystal of dimensions 40×40×10 mm3 together with the new large area position-sensitive photo multiplier tube (PSPMT) H8500 from Hamamatsu. The influence of Compton scattering on the DOI determination was also estimated by MC simulations. Altogether, we obtained ≤ 5 mm DOI resolution. PACS: 87.57.Ce, 87.58.Fg, 87.62.+n, 07.85.-m. View full abstract»

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  • Small animal imaging by single photon emission using pinhole and coded aperture collimation

    Publication Year: 2005 , Page(s): 573 - 579
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB) |  | HTML iconHTML  

    The design of detectors for radio-imaging of small animals is challenging because of the high spatial resolution required, possibly coupled with high efficiency to allow dynamic studies. Spatial resolution and sensitivity are difficult to attain at the same time with single photon imaging techniques because collimators define and limit performance. In this paper we first describe a simple desktop gamma imager equipped with a pinhole collimator and based on a pixellated NaI(Tl) scintillator array coupled to a Hamamatsu R2486 PSPMT. The limits of such a system as well as the way to overcome them in future systems is shown next. Better light sampling at the anode level would allow better pixel identification for a higher number of pixels, which is one of the parameters defining image quality and improving spatial resolution. The performance of such a design is compared with other designs using other PSPMT types with different light sampling schemes at the anode level. Finally, we show how the substitution of the pinhole collimator with a coded aperture collimator can result in a substantial improvement in system sensitivity while maintaining very good spatial resolution, possibly at a sub-millimeter level. Calculations and simulations of a particular solution show that sensitivity can improve by a factor of nearly 30. View full abstract»

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  • Photon-counting gamma camera based on an electron-multiplying CCD

    Publication Year: 2005 , Page(s): 580 - 588
    Cited by:  Papers (25)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1368 KB) |  | HTML iconHTML  

    We have developed a compact ultra-high-resolution gamma camera (UGC), based on an electron-multiplying charge-coupled device (EMCCD) coupled to a columnar CsI(Tl) scintillator. The EMCCD is suitable for photon-counting gamma-camera imaging, since it has an extremely low readout noise, even at high frame rates (<1 electron/pixel at 50 images/s or 11 Mpixel/s). The high frame rate prevents overlapping of scintillation events and reduces the accumulation of dark current noise. In this paper, we describe the drive- and readout electronics of the EMCCD, the image processing hardware and software, and the first ultra-high-resolution gamma-ray images obtained with the UGC. A digital signal processor (DSP) facilitates real-time frame analysis, comprising photon counting and energy discrimination, and reduces the data stream from 162 kB per frame to 8 B per detected scintillation event (i.e., for a typical application in multipinhole single photon emission computed tomography (SPECT) a data reduction from 28 GB/h by a factor of 20 000 to 1.4 MB/h). Such a reduced data stream is needed for applications that require the use of a large number of gamma cameras simultaneously. The image processing hardware that we describe allows the images from the EMCCD to be processed in real-time, at a rate of 50 images per second. First gamma-camera images with a spatial resolution as good as 60 μm full-width of half-maximum (FWHM) are shown. The prototype UGC allows for photon counting without the need for an image intensifier and has energy discriminating capabilities. View full abstract»

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  • Factors limiting the performance of CdZnTe detectors

    Publication Year: 2005 , Page(s): 589 - 598
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    In the past few years, significant progress has been achieved in the development of room-temperature semiconductor detectors, particularly those based on CdZnTe (CZT) crystals. Several types of electron-transport-only detectors have been developed: pixel, coplanar-grid, cross-strip, drift-strip, orthogonal coplanar strip, and virtual Frisch grid, many of which are now commercially available. Despite all these varieties in the detector designs, they have many common features and problems. This review summarizes the common detector design constraints and related factors limiting performance of CZT detectors: bulk and surface leakage currents, surface effects, properties of Schottky contacts and surface interfacial layers, charge sharing and loss in multielectrode devices, charge transport nonuniformities, and fluctuations in the pulse height for long-drift-length devices. We also describe unique capabilities at Brookhaven National Laboratory, Upton, NY, for CZT device characterization and recent progress utilizing these tools. View full abstract»

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  • Investigation of the "Block Effect" on spatial resolution in PET detectors

    Publication Year: 2005 , Page(s): 599 - 605
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1576 KB) |  | HTML iconHTML  

    Previous studies suggest that when block detectors are used in positron emission tomography (PET) scanners, a "block effect" of about 2 mm should be added in quadrature to the other effects blurring spatial resolution (SR). However, no explanation of the cause of the effect has ever been published. If the effect could be identified, isolated, and reduced then the SR of PET scanners should improve. We studied the origin of the "block effect", using experiments in which all other blurring effects on SR were minimized and precisely determined. Thin, 1 mm wide bismuth germanate (BGO) crystals and a small (1 mm) 68Ge source were used to probe the SR of a HR+ block detector. Two precise translation stages were used to move detectors. We compared coincidence aperture functions (CAFs) for crystals in the block with CAFs of single crystals of various widths. From those measurements, done with one block detector, we concluded that the central crystals in the block showed an additional blurring of 0.8 mm whereas the edge ones showed no additional blurring. When the detectors were separated by 21 cm, the full width at half maximum (FWHM) for central crystals was found to be 2.20±0.04 mm and for edge crystals 1.98±0.04 mm. The FWHM for 4.4 mm width crystals (as used in the HR + block) was estimated to be 2.1±0.2 mm. Results from the crystal identification matrix show that the apparent centroids of the crystals are not located at the geometric centers, which would give errors in the reconstruction algorithm assumed uniform sampling. Our results suggest that the additional blurring previously reported in PET scanners with block detectors is not entirely due to the use of block detectors. View full abstract»

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  • 3D-position-sensitive compact scintillation detector as absorber for a Compton-camera

    Publication Year: 2005 , Page(s): 606 - 611
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB) |  | HTML iconHTML  

    An absorption detector based on scintillator material and position-sensitive photomultipliers for a high resolution Compton-Camera prototype has been developed. The design of the Compton-Camera puts several demands on the absorption detector. For coincidence measurements it is necessary to have a very fast trigger signal and a fast signal output, due to the high rate of events. The energy of the primary photons requires the use of a thick scintillator block as an absorber, causing the problem of parallax effects in event reconstruction. Therefore a 3D-position resolution of the interaction point is needed. This is achieved by using position-sensitive photomultiplier tubes (PS-PMTs) for the readout of the scintillator. The design specifications and the performance of the complete detector will be presented in this paper. View full abstract»

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  • 3D imaging of microscopic structures using a proton beam

    Publication Year: 2005 , Page(s): 612 - 617
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (800 KB) |  | HTML iconHTML  

    The use of a 1μm ion beam as a tomographic probe could constitute a powerful tool for displaying the 3D structure of samples a few tens or hundreds of micrometers thick in a nondestructive way. At the Centre d'Etudes Nucle´aires de Bordeaux-Gradignan (CENBG), Gradignan, France, ion beam microtomography has been developed for biomedical applications at the cell level. The internal structure of cancer cells has been explored using scanning transmission ion microscopy (STIM) tomography, giving access to the 3D distribution of mass density (in g/cm3) within the analyzed volume. The sole sample preparation required is cryofixation and freeze-drying, permitting under vacuum analysis. The combination of STIM and particle induced X-ray emission (PIXE) tomography is under progress with the aim of revealing the distributions and local concentrations of elements at the cell level. View full abstract»

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  • Rapid computation of LROC figures of merit using numerical observers (for SPECT/PET reconstruction)

    Publication Year: 2005 , Page(s): 618 - 626
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB) |  | HTML iconHTML  

    The assessment of positron emission tomography (PET) and single photon emission computed tomography (SPECT) image reconstructions by image quality metrics is typically time consuming, even if methods employing model observers and samples of reconstructions are used to replace human testing. We consider a detection task where the background is known exactly and the signal is known except for location. We develop theoretical formulas to rapidly evaluate two relevant figures of merit: the area under the localization receiver operating characteristic (LROC) curve and the probability of correct localization. The formulas can accommodate different forms of model observer. The theory hinges on the fact that we are able to rapidly compute the mean and covariance of the reconstruction. For four forms of model observer, the theoretical expressions are validated by Monte Carlo studies for the case of MAP (maximum a posteriori) reconstruction. The theory method affords a 102-103 speedup relative to methods in which model observers are applied to sample reconstructions. View full abstract»

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  • Monte Carlo Simulation for the ECAT EXACT HR+ system using GATE

    Publication Year: 2005 , Page(s): 627 - 633
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (960 KB) |  | HTML iconHTML  

    GATE (Geant4 Application for Tomographic Emission) is a Monte Carlo simulation platform for nuclear medicine imaging, based on the Geant4 toolkit package. In order to improve data analysis and image quantification, a new simulator for the ECAT EXACT HR+ scanner was originally developed with GATE. In this study, we validate GATE simulations for positron emission topography (PET) imaging systems: a good agreement is obtained between simulated and actual experimental results. Additional GATE applications are also presented in the paper: an implementation of the voxelized Hoffman phantom and an example of a MRI/PET coupling system for improving image resolution. View full abstract»

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  • CT acquisition using PET detectors and electronics

    Publication Year: 2005 , Page(s): 634 - 637
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB) |  | HTML iconHTML  

    The emergence of positron emission tomography/computerized tomography (PET/CT) multimodality imaging has provided the ability to sequentially obtain anatomic and functional information using adjacent PET and CT scanners without having to move the patient from the bed. To avoid the need for successive PET and CT scans, we have investigated the possibility of acquiring both the anatomic and functional images using the same detection system, based on PET detectors and electronics operated in photon-counting mode. The detector consisted of a high-luminosity LSO scintillator individually coupled to an avalanche photodiode (APD) to enable low-energy X-ray detection at a high-count rate. A simulator was set up to collect tomographic data using a monochromatic 60 keV source (241Am) to irradiate a phantom made of tissue-equivalent materials. The observed spatial resolution with this nonoptimized setup was better than 2 mm, demonstrating the capability to provide fairly accurate anatomical localization in CT counting mode. The three main constituents of biological tissues (bones, water, and air) could be clearly identified in the images with a dose significantly lower than with conventional CT operated in current mode. These preliminary results demonstrate the feasibility of dual-modality PET/CT imaging based on PET detectors and electronics, and suggest that substantial dose reduction would be possible by acquiring the CT image in photon-counting mode. View full abstract»

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  • A restraint-free small animal SPECT imaging system with motion tracking

    Publication Year: 2005 , Page(s): 638 - 644
    Cited by:  Papers (14)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1040 KB) |  | HTML iconHTML  

    We report on an approach toward the development of a high-resolution single photon emission computed tomography (SPECT) system to image the biodistribution of radiolabeled tracers such as Tc-99m and I-125 in unrestrained/unanesthetized mice. An infrared (IR)-based position tracking apparatus has been developed and integrated into a SPECT gantry. The tracking system is designed to measure the spatial position of a mouse's head at a rate of 10-15 frames per second with submillimeter accuracy. The high-resolution, gamma imaging detectors are based on pixellated NaI(Tl) crystal scintillator arrays, position-sensitive photomultiplier tubes, and novel readout circuitry requiring fewer analog-digital converter (ADC) channels while retaining high spatial resolution. Two SPECT gamma camera detector heads based upon position-sensitive photomultiplier tubes have been built and installed onto the gantry. The IR landmark-based pose measurement and tracking system is under development to provide animal position data during a SPECT scan. The animal position and orientation data acquired by the tracking system will be used for motion correction during the tomographic image reconstruction. View full abstract»

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  • Implementation of an analytically based scatter correction in SPECT reconstructions

    Publication Year: 2005 , Page(s): 645 - 653
    Cited by:  Papers (19)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (864 KB) |  | HTML iconHTML  

    Photon scattering is one of the main effects contributing to the degradation of image quality and to quantitative inaccuracy in nuclear imaging. We have developed a scatter correction based on a simplified version of the analytic photon distribution (APD) method, and have implemented it in an iterative image reconstruction algorithm. The scatter distributions generated using this approach were compared to those obtained using the original APD method. Reconstructions were performed using computer simulations, phantom experiments, and patient data. Images corrected for scatter, attenuation, and collimator blurring were compared to images corrected only for attenuation and collimator blurring. In the simulation studies, results were compared to an ideal situation in which only the primary (unscattered) photon data were reconstructed. Results showed that in all cases, the scatter-corrected images demonstrated substantially improved image contrast relative to no scatter correction. For simulated data, scatter-corrected images had very similar contrast and noise properties to the primary-only reconstructions. Additional work is required to further reduce the computation times to clinically viable amounts. View full abstract»

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  • Accelerating popular tomographic reconstruction algorithms on commodity PC graphics hardware

    Publication Year: 2005 , Page(s): 654 - 663
    Cited by:  Papers (80)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB) |  | HTML iconHTML  

    The task of reconstructing an object from its projections via tomographic methods is a time-consuming process due to the vast complexity of the data. For this reason, manufacturers of equipment for medical computed tomography (CT) rely mostly on special application specified integrated circuits (ASICs) to obtain the fast reconstruction times required in clinical settings. Although modern CPUs have gained sufficient power in recent years to be competitive for two-dimensional (2D) reconstruction, this is not the case for three-dimensional (3D) reconstructions, especially not when iterative algorithms must be applied. The recent evolution of commodity PC computer graphics boards (GPUs) has the potential to change this picture in a very dramatic way. In this paper we will show how the new floating point GPUs can be exploited to perform both analytical and iterative reconstruction from X-ray and functional imaging data. For this purpose, we decompose three popular three-dimensional (3D) reconstruction algorithms (Feldkamp filtered backprojection, the simultaneous algebraic reconstruction technique, and expectation maximization) into a common set of base modules, which all can be executed on the GPU and their output linked internally. Visualization of the reconstructed object is easily achieved since the object already resides in the graphics hardware, allowing one to run a visualization module at any time to view the reconstruction results. Our implementation allows speedups of over an order of magnitude with respect to CPU implementations, at comparable image quality. View full abstract»

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  • Attenuation correction for the NIH ATLAS small animal PET scanner

    Publication Year: 2005 , Page(s): 664 - 668
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB) |  | HTML iconHTML  

    We evaluated an analytic attenuation correction method for the National Institutes of Health (NIH) Advanced Technology Laboratory Animal Scanner (ATLAS) small animal positron emission tomography (PET) scanner. This method is based on the body outline of emission images and an average empirical μ (linear attenuation coefficient) value. We evaluated this method using a computed tomography (CT)-based attenuation correction (ACs) as the "gold standard." A specially fabricated attenuation calibration phantom with cylindrical inserts that mimic different body tissues was used to derive the relationship to convert CT values to μ for PET. The methods were applied to three test data sets: 1) a uniform cylinder phantom, 2) the attenuation calibration phantom, and 3) a mouse injected with [18F]FDG. CT-based correction achieved activity restorations expected for all three data sets. The analytic method showed similar correction factors for the cylinder phantom and the mouse for which the attenuation medium volume matches the detectable emission source distribution. The correction factor for the attenuation calibration phantom was smaller because the emission image outline underestimated the attenuation medium volume. View full abstract»

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  • Diffusion regularization for iterative reconstruction in emission tomography

    Publication Year: 2005 , Page(s): 669 - 675
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB) |  | HTML iconHTML  

    We have recently proposed a regularized least square criterion for adaptive regularization of single photon emission computed tomography (SPECT) reconstruction with nonuniform attenuation correction. In the present study, we show that this regularization is closely related to a diffusion scheme used for Gaussian filtering. For a given value of the regularization parameter, the amount of smoothing is independent from the patient attenuation map, and it is mathematically related to the full-width at half-maximum (FWHM) of a Gaussian filter. A second regularized least square criterion is then derived for which regularization also behaves as a diffusion scheme. The new penalty is then shown to be also applicable to the weighted least square criterion, and to the Poisson maximum-likelihood criterion for positron emission tomography (PET) data (i.e., without attenuation) solved by the expectation maximization (EM) algorithm. For all these criteria, the regularization level can thus be set as the FWHM of a Gaussian filter. View full abstract»

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  • Improving the spatial resolution and image noise in densely pixilated detectors for positron emission mammography

    Publication Year: 2005 , Page(s): 676 - 683
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2216 KB) |  | HTML iconHTML  

    In positron emission mammography (PEM) sampling artifacts can be introduced from the use of discrete crystals which form planar stationary detectors. With the breast positioned in between the two detectors, the images are reconstructed by backprojecting lines of response (LORs) onto seven, equally spaced, virtual image planes. LORs are assumed to start and end on a unique point which is the centroid of interaction of gamma rays within each crystal. This effect limits the sampling of the image space and introduces gridlike sampling artifacts due to the variable density of LORs that intersect each pixel in the image. When using crystals that are very densely pixilated, as in PEM, the regions associated with each crystal in the crystal identification matrix may overlap. We postulate that by allowing the LORs to shift away from the centroid, toward the next most probable crystal element, sampling artifacts should be reduced. The solid angle function is an image uniformity correction function that corrects for the varying geometrical efficiencies of image pixels. The solid angle function is the last thing applied before the images are displayed. We postulate that by reordering the solid angle function and the smoothing algorithm, image quality should improve. Reformatting data from contrast resolution and point source phantom studies with the new strategies showed no or very few sampling artifacts. Contrast resolution measurements showed an improvement in both contrast and signal-to-noise ratio. In most cases point source measurements showed an improvement in spatial resolution and a reduction in noise. The clinical PEM images were reformatted with the new strategies where they showed no sampling artifacts and were smoother. The reformatted images were easier to interpret. View full abstract»

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  • Application of expectation maximization algorithms for image resolution improvement in a small animal PET system

    Publication Year: 2005 , Page(s): 684 - 690
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (896 KB) |  | HTML iconHTML  

    Modern positron emission tomography (PET) systems, offering high counting rate capabilities, high sensitivity, and near-submillimeter coordinate resolution, require fast image reconstruction software that can operate on list-mode data and take into account most of finite resolution effects such as photon scattering, positron range in tissue, and detector features. It has already been demonstrated that the expectation maximization (EM) method with extended system matrix modeling looks very attractive for image resolution recovery in PET imaging studies. In this paper, the performance of EM-based algorithms (in particular, their ability to improve the image resolution) is evaluated for a small animal PET imager with several phantoms. The achievement of a substantial decrease in processing time using an EM deblurring procedure is shown, as is an approach to successfully treat what are essentially nonspace-invariant resolution effects within a shift-invariant model. View full abstract»

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  • Architecture of a dual-modality, high-resolution, fully digital positron emission tomography/computed tomography (PET/CT) scanner for small animal imaging

    Publication Year: 2005 , Page(s): 691 - 696
    Cited by:  Papers (22)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB) |  | HTML iconHTML  

    Contemporary positron emission tomography (PET) scanners are commonly implemented with very large scale integration analog front-end electronics to reduce power consumption, space, noise, and cost. Analog processing yields excellent results in dedicated applications, but offers little flexibility for sophisticated signal processing or for more accurate measurements with newer, fast scintillation crystals. Design goals of the new Sherbrooke PET/computed tomography (CT) scanner are: 1) to achieve 1 mm resolution in both emission (PET) and transmission (CT) imaging using the same detector channels; 2) to be able to count and discriminate individual X-ray photons in CT mode. These requirements can be better met by sampling the analog signal from each individual detector channel as early as possible, using off-the-shelf, 8-b, 100-MHz, high-speed analog-to-digital converters (ADC) and digital processing in field programmable gate arrays (FPGAs). The core of the processing units consists of Xilinx SpartanIIe that can hold up to 16 individual channels. The initial architecture is designed for 1024 channels, but modularity allows extending the system up to 10 K channels or more. This parallel architecture supports count rates in excess of a million hits/s/scintillator in CT mode and up to 100 K events/s/scintillator in PET mode, with a coincidence time window of less than 10 ns full-width at half-maximum. View full abstract»

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  • Kinetic modeling of PET data without blood sampling

    Publication Year: 2005 , Page(s): 697 - 702
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB) |  | HTML iconHTML  

    In positron emission tomography (PET) imaging, application of kinetic modeling always requires an input curve (IC) together with the PET data. The IC can be obtained by means of external blood sampling or, in the case of cardiac studies, by means of a region-of-interest (ROI) drawn on the blood pool. It is, however, very unsuitable to withdraw and to analyze blood samples, and in small animals, these operations become difficult, while ICs determined from ROIs are generally contaminated by emissions from neighboring sites, or they are underestimated because of partial volume effect. In this paper, we report a new method to extract kinetic parameters from dynamic PET studies without a priori knowledge of the IC. The method is applied in human brain data measured with fluorodeoxyglucose (FDG) human-brain and in cardiac-rat perfusion studies with 13N-ammonia and 11C-acetate. The tissue blood volume (TBV), usually fitted together with the rate constants, is extracted simultaneously with the tissue time activity curves for cardiac studies, while for brain gray matter, TBV is known to be about 4% to 7%. The shape of IC is obtained by means of factor analysis from an ROI drawn around a cardiac tissue or a brain artery. The results show a good correlation (p<0.05) between the cerebral metabolic rate of glucose, myocardial blood flow, and oxygen consumption obtained with the new method in comparison to the usual method. In conclusion, it is possible to apply kinetic modeling without any blood sampling, which significantly simplifies PET acquisition and data analysis. View full abstract»

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    Publication Year: 2005 , Page(s): 703
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    Publication Year: 2005 , Page(s): 704
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