By Topic

Nuclear Science, IEEE Transactions on

Issue 1  Part 1 • Date Feb. 2005

Filter Results

Displaying Results 1 - 25 of 48
  • [Front cover]

    Page(s): c1
    Save to Project icon | Request Permissions | PDF file iconPDF (52 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Nuclear Science publication information

    Page(s): c2
    Save to Project icon | Request Permissions | PDF file iconPDF (47 KB)  
    Freely Available from IEEE
  • Table of contents

    Page(s): 1 - 3
    Save to Project icon | Request Permissions | PDF file iconPDF (82 KB)  
    Freely Available from IEEE
  • Depth-of-interaction recognition using optical filters for nuclear medicine imaging

    Page(s): 4 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    This paper describes a depth-of-interaction recognition method that can be applied to radiation detectors for positron emission tomography. The proposed method uses optical filters to differentiate wavelength distribution of scintillation photons depending on crystal depth positions. Then the crystal of interaction can be identified with a multianode photodetector whose sensitive surface is partly covered with optical filters. A validation experiment was performed with a position sensitive photomultiplier. As a result, it was proved that the crystal depth of interaction was clearly identified for photoabsorption events. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-dimensional array of scintillation crystals with proper reflector arrangement for a depth of interaction detector

    Page(s): 8 - 14
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1120 KB) |  | HTML iconHTML  

    A new method to acquire four-layer depth of interaction (DOI) information is proposed for the next generation positron emission tomography scanner (jPET-D4) that realizes high resolution and high sensitivity. The detector module of the jPET-D4 is a 16×16×4 Gd2SiO5: Ce (GSO) multicrystal array coupled with a 256 ch flat panel position sensitive photomultiplier tube (256 ch FP-PMT) having large opening area. The first challenge to encode DOI information was carried out with 8×8 array of units consisted of 2×2×4 crystal elements. The unit is developed for four-layer DOI encoding in previous report. Its crystal identification performance is evaluated by uniform gamma ray irradiation. The measured scintillation events are mapped on a two-dimensional (2-D) position histogram according to the relative ratio of the multianode output of the FP-PMT. However, peaks corresponding to the crystal elements of one unit form a colony in the resultant 2-D position histogram and there is large space between adjacent colonies. In the new method, the reflector arrangement which makes proper light sharing in the multicrystal array decreases such wasted space. Consequently, peak-to-valley on the 2-D position histogram was improved to 3.3:1 from 1.8:1. We found energy performance was also enhanced by the new method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of 256ch flat panel PS-PMT with small crystals for a DOI PET detector

    Page(s): 15 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1184 KB) |  | HTML iconHTML  

    A 256 channel flat panel position sensitive photomultiplier tube (256ch FP-PMT) was evaluated for application to a depth of interaction (DOI) PET detector composed of small crystal elements. The 256ch FP-PMT has 52 × 52 mm opening area with 89% useful area. Its 256 anodes are placed at a 3.04 mm interval. To estimate the FP-PMT performance, light spread functions of anodes at central and peripheral regions of a prototype 256ch FP-PMT were measured with a Gd2SiO5 (GSO) crystal sized 1.42 × 1.42 × 4.5 mm. The crystal cross section area is about one quarter of one anode area of the FP-PMT. It was found that light spread functions of peripheral anodes were similar to the functions of central anodes and also the functions measured with a 2.9 × 2.9 × 7.5 mm GSO crystal which has almost the same dimensions of cross-section as the anode area. Transit time fluctuation among the 256ch FP-PMT anodes was estimated by measuring time resolutions of a LuYSiO5 (LYSO) crystal at some central and peripheral positions. The LYSO crystal has the same dimensions as the smaller GSO crystal. BaF2 was used for a reference detector. The obtained distributions show about the same time resolution between the central and peripheral positions and the full width at half maximum is (366 ± 15) ps. The transit time fluctuation is ± 106 ps. Two-dimensional position histograms of a 32 × 32 GSO crystal array and two layers of 9 × 9 GSO crystal arrays are obtained by uniform gamma-ray irradiation. The crystal dimensions are 1.42 × 1.42 × 4.5 mm so that the 32 × 32 array covers all the useful area and indicates variation of crystal identification performance over the useful area. The 9 × 9 × 2 array is coupled to peripheral region. The resultant histograms confirm that a 256ch FP-PMT has enough capability for identifying crystals of this size even on the periphery and in DOI arrangement. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Compact readout electronics for position sensitive photomultiplier tubes

    Page(s): 21 - 27
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1200 KB) |  | HTML iconHTML  

    Two charge multiplexed readout schemes for position-sensitive photomultiplier tubes (PSPMTs) have been developed and evaluated. A two-stage split-charge method is compared to standard positional charge division. The resulting electronic circuits are highly compact and will be initially incorporated into a hand-held gamma ray imager for cancer staging. Electrical tests on the readout electronics are performed and intrinsic scintillation camera performance is evaluated using a 23 × 23 array of pixilated 2 × 2 × 3 mm3 LSO crystals coupled to a H8500 flat-panel PSPMT. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Readout of the optical PET (OPET) detector

    Page(s): 28 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    The design of an imaging system capable of detecting both high-energy γ-rays and optical wavelength photons is underway at the Crump Institute for Molecular Imaging. This system will noninvasively image small animal models in vivo for the presence of positron emission tomographic (PET) and optical signals. The detector will consist of modules of multichannel photomultiplier tubes (MC-PMT) coupled to arrays of scintillator crystals. The MC-PMT will detect both the photons produced due to bioluminescence and the photons generated by the interaction of γ-rays within the crystals. The long wavelength photons produced through bioluminescence are only slightly attenuated by these crystals and are detected directly at the photocathode of the MC-PMT, resulting in signals of small (5-10 mV) short (∼15 ns) pulses. In contrast, annihilation (511 keV) γ-rays interacting in the scintillator crystal send large bursts of photons to the PMT, and result in pulses that can be as large as 500 mV and > 200 ns duration. The processing of pulses with such different characteristics in a single circuit requires significant alteration of the standard pulse processing circuitry used in PET scanners. In this paper, we discuss the requirements of such a circuit and show the results of implementation of one design using single and multiple channel PMTs. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A block detector for a multislice, depth-of-interaction MR-compatible PET

    Page(s): 33 - 37
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB) |  | HTML iconHTML  

    We proposed and tested the a block detector for a multislice, depth-of-interaction (DOI) MR-compatible positron emission tomography (PET). The detector consists of a block detector, four optical fibers and photo-multiplier tubes (PMTs). The block detector is a lutetium oxyorthosilicate (LSO) DOI detector comprising eight LSOs arranged in a 2×2×2 matrix based on the concept proposed by Murayama et al. The size of a single scintillator of a prototype block detector was 2×2×2 mm. The scintillation photons are collected from the side of the scintillator block detector and are transferred to four channels of the position-sensitive PMT (PSPMT) using four optical fibers several meters long. The outputs of the PSPMT signals are calculated to determine the position of gamma interaction in the block detector. Results show that although the light loss from using the fiber was around 90%, there were sufficient transferred scintillation photons to obtain the photo-peak and to calculate the position of gamma interaction in the block detector with reasonable separation. We also modified the block detector to improve the performance of the detector. The size of a single scintillator of the modified block detector was enlarged to be 2.5 mm (transaxial) × 3.5 mm (axial) × 3.5 mm (depth) to improve the sensitivity. Good position responses as well as time resolution of 5.6-ns full-width at half-maximum (FWHM) were obtained for the modified block detector. With these results, we conclude that a two-rings, two-layer DOI-MR-compatible PET can be realized using the proposed block detector. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Examination of PbI2 and HgI2 photoconductive materials for direct detection, active matrix, flat-panel imagers for diagnostic X-ray imaging

    Page(s): 38 - 45
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    In this paper, the results of empirical studies of the dark current and X-ray signal response of thick, polycrystalline films of lead iodide (PbI2) and mercuric iodide (HgI2) are reported. These studies are being carried out as part of an extensive, integrated program of research to develop and incorporate such photoconductive, X-ray detection materials into direct detection, active matrix flat-panel imagers (AMFPIs) for applications in diagnostic imaging, as well as for radiotherapy imaging. Simple detector configurations incorporating these materials were prepared by physical vapor deposition (PVD) with thicknesses ranging from approximately 90 to 500 μm. For these detectors, the temporal behavior of the dark current and of the X-ray-induced photocurrent, under irradiation conditions relevant to fluoroscopy, radiography and mammography, were quantitatively examined and are reported. In addition, X-ray sensitivity results are also presented for a variety of conditions. The measurements were performed for externally applied electric fields ranging from 0.2 to 2.0 V/μm for both negative and positive polarities. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Digital autoradiography with a Medipix2 hybrid silicon pixel detector

    Page(s): 46 - 50
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (824 KB) |  | HTML iconHTML  

    A digital imaging system for beta and gamma autoradiography has been realized. It is a hybrid pixel detector based on a Medipix2 circuit (a single photon counting chip), developed at CERN in the framework of the Medipix2 European collaboration, as a successor of the Medipix1 chip. Medipix2 is realized in 0.25-μm CMOS technology; it has a sensitive area of 14 × 14 mm2 and a pixel pitch of 55-μm and is bump bonded to a 300-μm-thick silicon pixel detector. A test of this imaging system for digital autoradiography, with a detection threshold of about 6 keV, shows a noise in the order of 10-3 cps/mm2, a minimum detectable activity of 0.32 Bq in 14 h for 3H, and 0.012 Bq in 10 h for 14C. A preliminary spatial resolution test for 14C gives a full-width at half-maximum resolution of about 80 μm. Real-time images of 3H, 14C, 125I autoradiographic microscales are shown, and a comparison with existing experimental devices is presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Motion-compensated reconstruction of tomographic image sequences

    Page(s): 51 - 56
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB) |  | HTML iconHTML  

    In this paper, we study a motion-compensated approach for simultaneous reconstruction of image frames in a time sequence. We treat the frames in a sequence collectively as a single function of both space and time, and define a temporal prior to account for the temporal correlations in a sequence. This temporal prior is defined in a form of motion-compensation, aimed to follow the curved trajectories of the object motion through space-time. The image frames are then obtained through estimation using the expectation-maximization (EM) algorithm. The proposed algorithm was evaluated using the four-dimensional (4-D) gated mathematical cardiac-torso (gMCAT) D1.01 phantom to simulate gated single photon emission computed tomography (SPECT) perfusion imaging with Tc-99m-sestamibi. Our experimental results demonstrate that the use of motion compensation for reconstruction can lead to significant improvement in image quality and reconstruction accuracy. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Noise propagation in iterative reconstruction algorithms with line searches

    Page(s): 57 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB) |  | HTML iconHTML  

    In this paper, we analyze the propagation of noise in iterative image reconstruction algorithms. We derive theoretical expressions for the general form of preconditioned gradient algorithms with line searches. The results are applicable to a wide range of iterative reconstruction problems, such as emission tomography, transmission tomography, and image restoration. A unique contribution of this paper compared to the previous work is that the line search is explicitly modeled and we do not use the approximation that the gradient of the objective function is zero. As a result, the accuracy of the theoretical prediction is significantly improved. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An adaptation of ridge regression for improved estimation of kinetic model parameters from PET studies

    Page(s): 63 - 68
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    The quantitative analysis of dynamic positron emission tomography (PET) data to obtain kinetic constants in compartmental models involves the use of nonlinear weighted least squares regression. Current estimation techniques often have poor mean square error estimation properties. Ridge regression is a technique that has been found to have potential for improving mean square error when adapted to the nonlinear PET estimation problem. The effectiveness of ridge regression in this context, however, relies heavily on the correct selection of an unknown biasing parameter and the precise specification of a penalty function. In this study, an approach is explored for improving the effectiveness of ridge regression by incorporation of more rigorous Bayesian formulations for specification of the ridge penalty function. Using a variance component model, a prior covariance for the ridge penalty term is developed. An adaptive approach to the selection of the biasing parameter is also evaluated. The adaptive selection of the biasing parameter was not shown to improve estimation over more standard ridge estimation techniques. Ridge regression with the Bayesian formulation for the penalty, however, reduces current ridge regression parameter loss by up to 16% when the penalty closely reflects the true kinetic parameter covariance structure and performs comparably to the current method when the penalty does not. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of reconstruction and filtering on kinetic parameter estimation bias and reliability for dynamic SPECT: a simulation study

    Page(s): 69 - 78
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB) |  | HTML iconHTML  

    Dynamic SPECT has the potential to provide absolute physiological parameter estimates. However, the low sensitivity of SPECT typically results in very noisy dynamic SPECT data. Filtering can reduce the noise, but at the expense of degrading the already poor resolution further. The effect of reconstruction parameters, post-reconstruction filtering and resolution recovery on kinetic parameter estimation bias and reliability was systematically investigated. Dynamic projection data were generated using Monte Carlo (MC) simulations of a mathematical brain phantom at 10 different levels of Poisson noise. The projection data were reconstructed with OSEM with varying numbers of iterations and subsets and were filtered with three-dimensional (3-D) Gaussian filters with varying FWHM. Bias and reliability of the main parameters of interest (K1,Vd, and binding potential) for thalamus, cerebellum, and frontal cortex were estimated for the three-compartment model fits to the tissue time-activity curves derived from the reconstructed data. Reliability (standard deviation) of parameter estimates was obtained with the Bootstrap MC technique, which showed good agreement with conventional MC in a subset of data sets, but required only a small fraction of conventional MC computation time. Post-reconstruction filtering increased bias, without improving the reliability of parameter estimates and, hence, no post-reconstruction filtering is recommended. For reconstructions without resolution recovery, an effective number of 40 iterations overall provided the best tradeoff between bias and reliability for the range of noise levels studied. Resolution recovery achieved a modest reduction in bias. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Graph-based Mumford-Shah segmentation of dynamic PET with application to input function estimation

    Page(s): 79 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (896 KB)  

    A graph-theoretic three-dimensional (3-D) segmentation algorithm based on Mumford-Shah energy minimization is applied to the segmentation of brain 18F-fluoro-deoxyglucose (FDG) dynamic positron emission tomography data for the automated extraction of tissues with distinct time activity curves (TACs), and, in particular, extraction of the internal carotid arteries and venous sinuses for the noninvasive estimation of the input arterial TAC. Preprocessing by principal component analysis (PCA) and a Mahalanobis distance metric provide segmentation based on distinct TAC shape rather than simply activity levels. Evaluations on simulation and clinical FDG brain positron emission tomography (PET) studies demonstrate that differing tissue types can be accurately demarcated with superior performance to k-means clustering approaches, and, in particular, the internal carotids and venous sinuses can be robustly segmented in clinical brain dynamic PET datasets, allowing for the fully automatic noninvasive estimation of the arterial input curve. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The ECAT HRRT: an example of NEMA scatter estimation issues for LSO-based PET systems

    Page(s): 90 - 94
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    The ECAT high-resolution research tomograph (HRRT) is a three-dimensional (3-D)-only dedicated brain positron emission tomograph with LSO and GSO scintillators. In this paper, the system has been looked at as an example of issues that need to be addressed when evaluating LSO-based system following the recent NEMA NU 2-2001 protocols. The LSO scintillators contain the isotope 176Lu which is radioactive and creates a small amount of single counts and, depending on the low level discriminator threshold for validated singles, also true coincidence events from a cascade of gamma rays following the beta decay of 176Lu into 176Hf. The presence of intrinsic random and true coincidence events has an effect on the scatter fraction determination if using the guidelines according to NU 2-2001. We show here that these guidelines have to be changed in order to obtain accurate determination of the scatter fraction. In this paper, we have determined the scatter fraction for different low level discriminator settings. Since the scatter fraction determinations also comprise full count rate studies for the NEMA phantom, we have in addition extracted the sensitivity information for singles, true + scatter, and for the NEC data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Using the bootstrap method to evaluate image noise for investigation of axial collimation in hybrid PET

    Page(s): 95 - 101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB) |  | HTML iconHTML  

    The purpose of this paper was to investigate the use of the bootstrap method to evaluate noise in three-dimensional (3-D) ordered-subsets expectation-maximization list-mode iterative reconstructions from data simulated on a hybrid positron emission tomography (PET) system. In addition, image noise from reconstructions acquired with various levels of axial collimation was investigated. A warm cylinder (20-cm diameter and 70-cm long) was simulated using the GEANT 3.21 Monte Carlo simulation code for different collimator designs: open-frame (OPEN), parallel (PAR) axial, and hybrid parallel fan-beam (HPF) axial collimators. Twenty noisy sets of list-mode data were simulated for each collimator. In addition, events from the first noisy list-mode data set of each category (OPEN, PAR axial, and HPF axial collimators) were chosen at random with replacement to produce twenty new sets of the same size. List-mode data were reconstructed using a 3-D ordered-subsets expectation-maximization (OSEM) list-mode iterative reconstruction algorithm using two subsets and up to 10 iterations. The standard deviations within volumes of interest (VOIs) were computed, and the mean value of this estimate over noise realizations was evaluated. The results indicate that there is no statistical significant difference in the standard deviation of VOI estimates from noisy realizations and bootstrap samples when using the OPEN, the PAR axial, and the HPF axial collimators. The results showed that the precision of VOI estimates varies with the axial spatial location within the object and the axial collimator. In addition, noise variation within list-mode reconstructed images appears to be related to the 3-D sensitivity map. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • GePEToS: a Geant4 Monte Carlo simulation package for positron emission tomography

    Page(s): 102 - 106
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB) |  | HTML iconHTML  

    GePEToS is a simulation framework developed over the last few years for assessing the instrumental performance of future positron emission tomography (PET) scanners. It is based on Geant4, written in object-oriented C++ and runs on Linux platforms. The validity of GePEToS has been tested on the well-known Siemens ECAT EXACT HR+ camera. The results of two application examples are presented: the design optimization of a liquid Xe μPET camera dedicated to small animal imaging as well as the evaluation of the effect of a strong axial magnetic field on the image resolution of a Concorde P4 μPET camera. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Septa design for a prostate specific PET camera

    Page(s): 107 - 113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB) |  | HTML iconHTML  

    The recent development of new prostate tracers has motivated us to build a low cost PET camera optimized to image the prostate. Coincidence imaging of positron emitters is achieved using a pair of curved detector banks. The bottom bank is fixed below the patient bed, and the top bank (which is above the patient) moves upward for patient access and downward for maximum sensitivity. In this paper, we study the design of septa for the prostate camera using Monte Carlo simulations. The system performance is measured by the detectability of a prostate tumor and by the conventional noise equivalent count (NEC). We have studied 27 septa configurations. The results show that septa design has a large impact on the lesion detection at a given activity concentration. At the background activity level of 0.1 μCi/cc, sparse septa with 8-crystal spacing outperforms the traditional two-dimension (inter-plane septa) and three-dimension (septaless) designs in terms of both the lesion detection and NEC. Significant differences are observed between the lesion detectability and NEC performance, indicating that the NEC may not be suitable for this lesion detection task. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Printed sources for positron emission tomography (PET)

    Page(s): 114 - 118
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    We have developed a method that allows manufacturing of 18F radioactive printed sources using a standard ink-jet printer. Although previously used in printing and imaging single gamma emitter sources, such techniques have not been, to our knowledge, applied to the manufacturing of positron emitting sources. The added complication in the latter instance is a nonzero positron range and, thus, the need for some attenuating material surrounding the positron emitting atoms. The point sources were first imaged on a phosphor imager and then scanned on three different tomographs (Siemens/CTI ECAT 953B, CPS high-resolution research tomograph (HRRT) and Concorde microPET R4) to measure their point spread functions (PSFs). Where appropriate, the resolution agrees with published values. A comparison of the full width and tenth width half maxima of the point source profiles obtained with and without additional attenuating material showed no effect of the additional attenuation material on their values. The presence of the attenuating material however increased the number of counts in the point source image several fold due to a larger fraction of the positrons annihilating in the region close to the printed source. The results show that printed sources either on paper alone or on paper sandwiched between some additional attenuating material provide a practical means to obtain positron emitting sources. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Gantry design with accurate crystal positioning for a high-resolution transformable PET camera

    Page(s): 119 - 124
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1712 KB) |  | HTML iconHTML  

    A positron emission tomography (PET) camera capable of transforming its geometric configuration is being developed. This high-resolution oncologic transformable PET (HOTPET) can be modified from a large detector ring of 83 cm to a small diameter ring of 54 cm. The system consists of 12 rectangular detector modules arranged in a polygon. The detector gap between modules remains constant in both configurations because each module is rotated around its own axis and displaced radially, bringing together adjacent modules. HOTPETs detectors are highly pixilated (crystal pitch 2.6 mm), requiring accurate placement of the modules relative to each other to ensure alignment of crystals within the same detector ring. We have designed a precise detector bank holder with keyways and complementary keys built onto its sides to allow interlocking with each other to form a polygon and maintain crystal coplanarity. Consequently, we were able to design the gantry supporting the modules using wider tolerances and so reduce its construction cost. The module provides support to 77 photomultiplier tubes (PMTs), the analog front-end electronics, and an automated PMT-gain control, all enclosed within a controlled environment. Potential development of light leaks was minimized with only two parting surfaces throughout the module's box, and tortuous-path air ducts inside the walls. Internal airflow allows temperature control. Simple removal of a back cover and a motherboard gives access to any part of the electronic components or a PMT with minimal disturbance to other components. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A simple respiration gating technique and its application in high-resolution PET camera

    Page(s): 125 - 129
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB) |  | HTML iconHTML  

    We have developed a simple technique to gate positron emission tomography (PET) imaging in synchronization with respiratory motion to reduce image blurring caused by breathing and to improve quantification of tracer uptake in lesions in the chest and abdomen, especially in very high-resolution PET systems. Taking advantage of the temperature differences in the air flow in a nostril due to inhalations and exhalations, a simple solid-state thermometer was used to construct a respiratory gating system to monitor the respiratory cycles. The gating system provided trigger signals indicating inspiration and expiration as well as periodic (about 40 Hz) timing-tick signals. These trigger and timing-tick signals were inserted into the data stream in real-time while the PET camera was taking data. The gating trigger signals represent particular phases of respiratory motion. This gating system was implemented and tested with our MDAPET, a very high-resolution (2.7-mm resolution) PET camera developed at The University of Texas M. D. Anderson Cancer Center. A volunteer with two spherical lesion phantoms (diameters 3 mm and 5 mm) placed on the abdomen close to the navel was scanned in the gated mode. The respiration-gated images of the lesion phantoms were compared and studied. The simple respiratory gating system worked well in terms of detecting the breathing cycle and providing gating trigger and timing-tick signals. Image blur and errors in the measurements of the lesions' volumes in the gated PET images were reduced, compared with those of the nongated PET images. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Relative renal blood flow measurements with Rb-82 and a hybrid gamma camera using a pig model

    Page(s): 130 - 135
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB) |  | HTML iconHTML  

    We have successfully demonstrated with chronically implanted blood flow probes in a pig model that renal uptake of Rb-82 is indeed sensitive to acute renal blood flow changes. Two flow probes were placed around the left and right renal arteries in a surgical procedure nine weeks before the first Rb-82 measurements. Together with the flow probes, a flow restrictor was implanted around the left renal artery. Single bolus infusions of 6 mCi Rb-82 were used to study the uptake in the kidneys approximately 7 minutes apart in hybrid-image limited-angle acquisitions (stationary camera heads posterior and anterior of the pig) while changing the flow to the left kidney between acquisitions. The acquired data were reconstructed into 7.5-s frames using a maximum likelihood (ML) list-mode reconstruction algorithm exploiting timing signals inserted into the list every 0.25 s. Reconstructed data were orientated to coronal views before regions of interest (ROIs) were drawn over both kidneys with a separate background region for each. The data represented are noisy due to the reconstructed 7.5-s frames, and the total imaging time of 5 min (or 4 Rb-82 half-lives). We were able to show a steady decline in uptake of Rb-82 in the left kidney that correlates with the reduction in renal blood flow. The reduced blood flow to the left kidney affects the Rb-82 uptake to the right kidney slightly, while blood flow decreased up to 33%. Comparing the baseline renal blood flow of the left kidney obtained before and after the intervention indicates that some ischemia persists after blood flow was restored. Attenuation compensation better described the contour of the kidney but only scales the time activity curve without changing its shape. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Lesion detectability and quantification in PET/CT oncological studies by Monte Carlo simulations

    Page(s): 136 - 142
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1720 KB) |  | HTML iconHTML  

    The aim of this work was to assess lesion detectability and quantification in whole body oncological 18F-FDG studies performed by a state-of-the-art integrated Positron Emission Tomograph/computed tomography (PET/CT) system. Lesion detectability and quantification were assessed by a Monte Carlo (MC) simulation approach as a function of different physical factors (e.g., attenuation and scatter), image counting statistics, lesion size and position, lesion-to-background radioactivity concentration ratio (L/B), and reconstruction algorithms. The results of this work brought to a number of conclusions. The MC code PET-electron gamma shower (EGS) was accurate in simulating the physical response of the considered PET/CT scanner (>90%). PET-EGS and patient-derived phantoms can be used in simulating18 F-FDG PET oncological studies. Counting statistics is a dominant factor in lesion detectability. Correction for scatter (from both inside and outside the field of view) is needed to improve lesion detectability. Iterative reconstruction and attenuation correction must be used to interpret clinical images. Re-binning algorithms are appropriate for whole-body oncological data. A MC-based method for correction of partial volume effect is feasible. For the considered PET/CT system, limits in lesion detectability were determined in situations comparable to those of real oncological studies: at a L/B=3 for lesions of 12 mm diameter and at a L/B=4 for lesions of 8 mm diameter. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Paul Dressendorfer
11509 Paseo del Oso NE
Albuquerque, NM  87111  USA