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Nuclear Science Symposium Conference Record, 2000 IEEE

Date 15-20 Oct. 2000

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  • 2000 IEEE Nuclear Science Symposium Conference [front matter]

    Publication Year: 2000 , Page(s): 0_1 - 0_16
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  • Scientific consultancy experiences by CAT-SCIENCE-Bt, Hungary [in fusion plasma physics]

    Publication Year: 2000
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    Summary form only given. CAT-SCIENCE Bt, has been working since summer 1998 as a scientific consultancy company in the field of experimental fusion plasma physics. The strategic idea of the company is to use the special knowledge of researchers in governmental institutions by involving them in limited time projects as external experts. We think that in this way we enhance knowledge transfer from the academic to the industrial sector. A special problem of R&D companies in Eastern Europe is the lack of capital on the other hand the advantage is the relatively low staff costs. Taking these into account the company aims at providing services in special fields in R&D View full abstract»

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  • A parallel Monte Carlo code for planar and SPECT imaging: implementation, verification and applications in 131I SPECT

    Publication Year: 2000 , Page(s): 20/30 - 20/34 vol.3
    Cited by:  Papers (1)
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    This paper reports the implementation of the SIMIND Monte Carlo code on a IBM SP2 distributed memory parallel computer. Basic aspects of running Monte Carlo particle transport calculations on parallel architectures are described. The authors' parallelization is based on equally partitioning photons among the processors and uses the Message Passing Interface (MPI) library for interprocessor communication and the Scalable Parallel Random Number Generator (SPRNG) to generate uncorrelated random number streams. These parallelization techniques are also applicable to other distributed memory architectures. A linear increase in computing speed with the number of processors is demonstrated for up to 32 processors. This speed-up is especially significant in Single Photon Emission Computed Tomography (SPECT) simulations involving higher energy photon emitters, where explicit modeling of the phantom and collimator is required. For 131I, the accuracy of the parallel code is demonstrated by comparing simulated and experimental SPECT images from a heart/thorax phantom. Clinically realistic SPECT simulations using the voxel-man phantom are carried out to assess scatter and attenuation correction View full abstract»

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  • Performance measurement of a new high resolution detector system for I-131 thyroid studies

    Publication Year: 2000 , Page(s): 22/35 - 22/37 vol.3
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    A 2-dimensional detector system for high resolution thyroid I-131 scintigraphy was developed. It has a sensitive area of 4 cm×4 cm and consists of a lead-collimator and an array of 10×10 EGO crystals combined with a position sensitive photomultiplier. The spatial resolution and the sensitivity of the detector has been measured and compared to two commercially available gamma-cameras. Furthermore first patient measurements have been carried out View full abstract»

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  • Influence of detector thickness on resolution in three-headed gamma camera PET

    Publication Year: 2000 , Page(s): 16/17 - 16/21 vol.3
    Cited by:  Papers (1)
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    In PET imaging with large area NaI scintillators, an uncertainty in the measured position of a photon hitting the detector at an oblique angle exists due to the thickness of the crystal in the detector. To evaluate the influence of the crystal thickness and the angle of incidence on the spatial resolution, simulations and measurements of a dual and triple headed PET system in different configurations were performed. In the simulations, the resolution was calculated as a function of: head radii, crystal thickness, head orientation and the maximum angle of incidence. The influence of these parameters (except crystal thickness) was also evaluated by measurements on a dual-headed AXIS and triple-headed IRIX PET systems. It was observed that reducing the average angle-of-incidence (and hence reducing the depth-of-interaction uncertainty) tended to improve the spatial resolution. This could be accomplished by restricting the maximum angle-of-incidence, increasing the separation of the heads, or changing the orientation of the heads (a 0-120-240 configuration has a greater average angle-of-incidence than a 0-90-180 or 0-180 configuration). However, when taking the effect of non-collinearity of the annihilation into account, increasing the separation of the heads results in a degrading resolution. The resolution improved by decreasing the crystal thickness (since depth-of-interaction uncertainty was reduced). The system sensitivity tended to decrease with the increase in resolution View full abstract»

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  • Description of a prototype combined CT-SPECT system with a single CdZnTe detector

    Publication Year: 2000 , Page(s): 16/1 - 16/5 vol.3
    Cited by:  Papers (1)  |  Patents (1)
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    The authors have developed a system that performs both X-ray CT and SPECT using a single CdZnTe detector. Their prototype employs a 9.6×9.6-mm2 CdZnTe detector with 1.5×1.5-mm2 pixellated anodes configured as a 4×4 array. Pulse counting electronics with short shaping time (50 ns) are used to satisfy requirements for high photon rates in X-ray imaging, and to achieve response linearity up to 4×105 counts per second per detector element. The measured energy resolution at 140 keV is 10.4%. The authors have characterized system performance by imaging a radiographic resolution phantom and the Hoffman Brain phantom. The spatial resolutions of CT and SPECT are about 1 mm and 9 mm, respectively. The sensitivity per detector area of radionuclide imaging is about one-half of that of a conventional imager. The registration of images from these two modalities is intrinsic since the imaging geometry is identical View full abstract»

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  • Slat collimation and cylindrical detectors for PET simulations using SimSET

    Publication Year: 2000 , Page(s): 20/89 - 20/92 vol.3
    Cited by:  Papers (1)
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    SimSET (a Simulation System for Emission Tomography) is a public domain simulation of PET and SPECT. The recently released version 2.6 adds capabilities to simulate slat collimation for dual-headed coincidence imaging (DHCl) and cylindrical detectors for positron emission tomography (PET). The slat collimator module simulates axial slats of attenuating material in front of planar detectors. The collimator may be composed of multiple materials and be radially layered. The cylindrical detector module simulates an annulus of detector material. The detector may also be composed of multiple materials, and may vary axially and radially, but transaxial cuts are not simulated. Validation tests compared results from slat collimator and cylindrical detector simulations to analytic predictions and to simulations using other previously tested SimSET modules. Beta testers have used both modules extensively View full abstract»

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  • Testing and modeling Ethernet switches and networks for use in ATLAS high-level triggers

    Publication Year: 2000 , Page(s): 26/45 - 26/49 vol.3
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    The ATLAS second level trigger will use a multilayered LAN network to transfer 5 Gbyte/s detector data from ~1500 buffers to a few hundred processors. A model of the network has been constructed to evaluate its performance. A key component of the network model is a model of an individual switch, reproducing the behavior measured in real devices. A small number of measurable parameters are used to model a variety of commercial Ethernet switches. Using parameters measured on real devices, the impact on the overall network performance is modeled. In the Atlas context, both 100 Mbit and Gigabit Ethernet links are required. A system is described which is capable of characterizing the behavior of commercial switches with the required number of nodes under traffic conditions resembling those to be encountered in the Atlas experiment. Fast Ethernet traffic is provided by a high density, custom built tester based on FPGAs, programmed in Handel-C and VHDL, while the Gigabit Ethernet traffic is generated using Alteon NICs with custom firmware. The system is currently being deployed with 32 100 Mbit ports and 16 Gigabit ports, and will be expanded to ~256 nodes of 100 Mbit and ~50 GBE nodes View full abstract»

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  • The LHCb DAQ system

    Publication Year: 2000 , Page(s): 26/1 - 26/6 vol.3
    Cited by:  Papers (2)
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    The LHCb experiment is the most recently approved of the 4 experiments under construction at CERN's LHC accelerator. It is a special purpose experiment designed to precisely measure the CP violation parameters in the B-B system. Triggering poses special problems since the interesting events containing B-mesons are immersed in a large background of inelastic p-p reactions. We therefore decided to implement a 4 level triggering scheme. The LHCb DAQ system will have to cope with an average trigger rate of ~40 kHz, after two levels of hardware triggers, and an average event size of ~150 kB. Thus an event-building network which can sustain an average bandwidth of 6 GB/s is required. A powerful software trigger farm will have to be installed to reduce the rate from the 40 kHz to ~200 Hz of events written to permanent-storage. In this paper we will concentrate on the networking aspects of the LHCb data acquisition and the control system View full abstract»

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  • Preliminary evaluation of the microPET P4: a PET system dedicated to small animal imaging

    Publication Year: 2000
    Cited by:  Papers (1)
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    Summary form only received as follows: The microPET Primate 4 ring system (P4) is a small animal PET tomograph with an 8 cm axial extent, an 18 cm transaxial field of view (FOV) and an animal port of 22 cm diameter. The system is comprised of 168 detectors, each with an 8×8 array of 2.2×2.2×10 mm LSO crystals, for 32 crystal rings with a detector diameter of 26 cm. The crystals of each detector are coupled to a Hamamatsu H5900-C8 position sensitive photomultiplier tube (PMT) via a 10 cm long fiber bundle. The reconstructed image resolution was measured with an F-18 line source positioned at different radial offsets [0-5 cm] across the FOV. The reconstructed radial and tangential components of the spatial resolution range from 2.3 mm at the center to 3.0 mm at 5 cm radial offset. The tomograph has peak system sensitivity of 1.7% at the center FOV with an energy window of 250-700 keV. The energy resolution of the individual crystal elements ranges from 22 to 34%, with a mean of 26%. A miniature Derenzo and a monkey brain phantom were scanned and reconstructed with filtered backprojection to illustrate the capabilities of the tomograph. Randoms subtraction was performed on all acquisitions View full abstract»

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  • State of the art in electronic detectors for portal imaging

    Publication Year: 2000
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    Summary form only given. The first clinically-practical, electronic portal imaging devices, which were introduced over a decade ago, spurred the exploration of the role of digital imaging in localization and verification for radiotherapy. However, these technologies, based on lens and fiber-optic-coupled phosphor-camera systems and on liquid ionization chambers, generally fail to provide imaging performance equivalent to that of the current gold standard, radiotherapy film cassettes. While incremental improvements in these technologies have been achieved, these and other limitations have encouraged the development of fully solid-state, digital imagers based on thin-film electronics. This new technology, referred to as active matrix, flat-panel imagers (AMFPIs), employs large monolithic imaging arrays (presently, up to 40×40 cm) and provides image quality superior to that of conventional film systems. AMFPIs are compact, allow radiographic or fluoroscopic readout, and provide images exhibiting a high degree of spatial and contrast information content over a wide range of doses and therapy energies. This technology also lends itself to diagnostic projection and CT imaging as well as dosimetry-all of which are being examined in the context of treatment room needs. In this presentation, the current status of electronic detectors for portal imaging is reviewed and anticipated future developments are discussed View full abstract»

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  • Correction for head movements in positron emission tomography using an optical motion tracking system

    Publication Year: 2000 , Page(s): 17/58 - 17/62 vol.3
    Cited by:  Papers (1)  |  Patents (3)
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    Methods capable of correcting for head motion in all six degrees of freedom have been proposed for PET brain imaging but not yet demonstrated in human studies. These methods rely on the accurate measurement of motion in a coordinate frame aligned with the scanner. We present methodology for the direct calibration of an optical motion tracking system to the reconstruction coordinate frame using paired coordinate measurements obtained simultaneously from a PET scanner and tracking system. We also describe the implementation of motion correction, based on the multiple acquisition frame method originally described by Y. Picard and C.J. Thompson (1997), using data provided by the motion tracking system. Effective compensation for multiple six degree-of-freedom movements is demonstrated in dynamic PET scans of the Hoffman brain phantom and a normal volunteer. We conclude that reduced distortion and improved quantitative accuracy can be achieved with this method in PET brain studies degraded by head movements View full abstract»

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  • Magnified hard X-ray microtomography

    Publication Year: 2000
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    Summary form only given. In the field of hard X-ray microtomography one goal is the enhancement of resolution. Several ways can be followed to obtain this objective. One possibility is the use of high-resolution X-ray films or detector screens coupled with a microscope optical system. The limitation of resolution is either given by the grain size of the X-ray film or the point spread function of the scintillator screen and the diffraction limit of the microscope. Tomography resolution can also be improved by magnified imaging of the object on the detector system. The appearance of X-ray lenses, such as Fresnel zone-plates, Bragg-Fresnel lenses and recently compound refractive lenses opened a large field for magnified imaging, similar to glass lenses for visible light. These new optical elements are already employed for X-ray imaging and can also be used for magnified microtomography. They have the potential of improving the resolution to a few hundred nanometers, which would overcome the resolution limits of current detectors. First tomography experiments with compound refractive lenses using a monochromatic beam as well as a so-called “pink” beam with a large energy bandwidth (DE/E=10-2 compared to DE/E=10-4 for a monochromatic beam) give promising results View full abstract»

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  • Evaluation of performance of dedicated, compact scintillation cameras

    Publication Year: 2000 , Page(s): 21/109 - 21/113 vol.3
    Cited by:  Papers (3)
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    As part of the development of dedicated scintillation cameras, the authors compared the performances of 2 dedicated cameras with a standard clinical camera (Siemens Orbiter). One dedicated camera was based on a single Position Sensitive Photomultiplier (PSPMT) coupled to a 6 cm by 6 cm by 6 mm NaI(Tl) crystal and the other was based on multiple-PSPMTs coupled to a 2 mm by 2 mm by 6 mm matrix of NaI(Tl) crystals. Spatial resolution was measured with all cameras as a function of depth. The ability of the cameras to measure small superficial tumors was tested with a phantom consisting of 6 hot cylindrical tumors of height 3 mm and varying diameters against a warm background. The tumors were imaged at various depths within the background using tumor to background activity concentration ratios of 10:1 and 5:1. The dedicated cameras show improved performance in imaging the breast tumor phantom, suggesting that these devices will have a role in scintimammography and assisting in O.R, procedures such as sentinel node dissection and other shallow depth of field applications View full abstract»

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  • DRR volume rendering using splatting in shear-warp context

    Publication Year: 2000 , Page(s): 19/12 - 19/17 vol.3
    Cited by:  Papers (1)
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    Digital Reconstruction Radiography (DRR) is an important technique in radiotherapy imaging applications. DRR volume rendering aims at rendering DRR images using CT or other tomographic data sets. In addition to the appropriate optical model, the interactive and realistic DRR imaging depends mainly on an accurate attenuation coefficient transfer function, which is usually a piecewise function, and an interactive rendering algorithm with reasonable rendering quality. In this paper, we first present a realistic DRR transfer function based on the mass attenuation coefficient composition. Then, we introduce an object space DRR rendering algorithm, DRR splatting in the sheared object space. The DRR image qualities under different rendering algorithms are compared, including ray casting, Fourier volume rendering, projective shear-warp and splatting shear-warp. Finally, a line encoding technique is adopted to accelerate DRR rendering View full abstract»

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  • Investigation of bias free positioning estimators the scintillation camera

    Publication Year: 2000 , Page(s): 20/25 - 20/28 vol.3
    Cited by:  Papers (1)
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    Bias free positioning estimators for scintillation cameras are investigated. A linear correlation coefficient (LCC) and Chi square error (CSE) method are evaluated with respect to linearity and spatial resolution performance. The LCC method uses correlation information between the true function (i.e., light response function) and measured data in mapping an event characterization vector to the associated position. The CSE method estimates position where the Chi-square error between two functions becomes minimized. In order to determine true statistics as a function of position, the light response function (LRF) was estimated based on sample measurements by using a cubic spline interpolation technique which provides smooth first order and continuous second order derivative of the LRF. Both methods have superior linearity properties compared to the weighted centroid. Each method can be considered as a bias free positioning estimator within the effective field of view of the detector, The spatial resolution performance of the CSE method is ~7% and ~16% better than the weighted centroid method for a 16 mm and 25 mm thick crystal, respectively. The spatial resolution performance of the LCC method is comparable to that of the weighted centroid method View full abstract»

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  • High-resolution absolute SPECT quantitation for I-131 distributions used in the treatment of lymphoma: a phantom study

    Publication Year: 2000 , Page(s): 18/2 - 18/6 vol.3
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    Clinical lymphoma I-131 radioimmunotherapy (RIT) studies are underway at the authors' institution. The effectiveness of treatment can be evaluated through accurate time dependent three-dimensional dosimetry calculations based on SPECT images. The authors compared the absolute quantitative SPECT performance of a high-resolution rotating parallel-hole collimator (RPHC) designed to minimize septal penetration with that of a traditional medium-energy parallel-hole collimator (MEPHC). They scanned a phantom consisting of 4 spheres having inner diameters of 2.2 and 2.8 cm and whose activity concentration ratios with respect to the surrounding medium were between 5:1 and 17:1. Images were reconstructed using the OSEM algorithm (10 subsets, 20 iterations) with spatial resolution modeling. Quantitation of the MEPHC SPECT images yielded a large overestimation of the surrounding activity concentration (50%) due to septal penetration. Quantitation of the RPHC SPECT image yielded a surrounding medium activity concentration within 8% of the expected value, and the activity within the spheres was estimated to within 20% of their absolute expected values, and 12% of their relative expected values. It is concluded that for the present quantitation application the benefits of septal penetration suppression by the RPHC outweigh the increased image noise due to low count rate. These results point to the feasibility of using a large field-of-view (FOV) collimator based on the imaging principles of the RPHC for accurate clinical SPECT quantitation of I-131 RIT View full abstract»

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  • Evaluation of a novel CCD camera for dose reduction in digital radiography

    Publication Year: 2000 , Page(s): 23/53 - 23/58 vol.3
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    Work is currently underway to investigate the application of a novel, low light level charge-coupled device to the field of digital radiography. The CCD has been developed by Marconi Applied Technologies. The image sensor in the camera is a frame transfer device with an image size of 576×288 pixels and a pixel size of 20×30 μm2 . The readout is standard 625-line video producing 25 frames per second at a pixel read out rate of 11.109 MHz. Images are captured using a digital image acquisition card. The CCD has increased sensitivity at low light levels and is able to operate at high levels of gain with the advantage of lower levels of noise in comparison with standard CCDs. For radiographic purposes a system based upon this device has the potential to operate at reduced irradiation levels. The overall aim of this work is to investigate dose savings in the field of fluoroscopy that may be achieved with this device. This paper presents an evaluation of the noise performance of the CCD. Some preliminary work to estimate dose levels in a simple CCD based imaging system is discussed View full abstract»

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  • Relative lesion detectability in 3D vs. 2D dedicated multi-ring PET

    Publication Year: 2000 , Page(s): 17/18 - 17/22 vol.3
    Cited by:  Papers (3)
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    The authors estimated the detectability of spheres of different sizes but equal activity contrast, embedded in a clinically realistic phantom in order to compare two-dimensional (2D) and three-dimensional (3D) whole-body (WB) PET imaging for a relevant diagnostic task. Five plastic spheres with inside diameters of 0.8 to 3.4 cm, containing 74 kBq/ml of Ge-68, were placed in an anthropomorphic torso phantom. The background organs contained F-18 activity concentrations in appropriate physiologic proportions, as did a head phantom positioned outside the field of view (FOV) of the authors' ECAT-HR+ system. The phantom was scanned for 9 hours at 1 bed position as the F-18 decayed from 97 to 3.2 kBq/ml. The authors obtained 10, 1-minute scans for each activity contrast level, alternating among 3 acquisitions: 2D mode with standard maximum ring difference (MRD=7), standard 3D mode (MRD=22), and 3D mode with MRD=13 (3D*). Images from 2D and 3D acquisitions were reconstructed by filtered backprojection and 3D reprojection (3DRP); 3D data were also reconstructed by FBP after Fourier rebinning (FORE+FBP). Sphere detectability was estimated using non-prewhitening (NPW) matched filtering to compute the detection signal-to-noise ratio, NPW SNR. In almost all cases, NPW-SNR was greater for 3D or 3D* than for 2D, although 2D outperformed 3D with 3DRP reconstruction at the earliest time points for 2 spheres located near opposite ends of the axial FOV; FORE+FBP reconstruction significantly improved the detectability of these spheres, compared to 3DRP, and demonstrated the expected near equivalence of 3D and 3D* data from spheres near the ends of the FOV. The authors' results were not predictable from global NEC considerations alone View full abstract»

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  • Scintillator crystal optimization by Monte Carlo simulation for photodiode matrix detector

    Publication Year: 2000 , Page(s): 20/16 - 20/19 vol.3
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    The design of gamma ray imaging probes based on silicon photodiodes and on a CsI(Tl) monocrystal is delicate and complex. Electronic and statistical noise deteriorate energy and spatial resolution. A Monte Carlo simulation is used to set the probe's parameters in order to obtain the best compromise between spatial uniformity energy uniformity, spatial linearity and energy collection. The output distribution of light depends on the physical properties of crystal edges, crystal thickness and refractive index of the coupling grease. A 75×75 mm2 squared CsI(Tl) crystal coupled to a 5 by 5 array of photodiodes (15×15 mm2) has been simulated. Energy and spatial characteristics of the probe were determined for crystal thickness varying from 2 mm and 20 mm and refractive index of coupling grease varying from 1.5 and 2.5. The influence of the aspect of the surfaces has also been studied. The best results were obtained with a crystal thickness of 8 mm, a grease refractive index of 1.9, and a crystal with polished edges and diffusing entrance face. These parameters minimize the statistic fluctuations of the light distribution on the array of photodiode leading to the best compromise between spatial linearity and energy collection View full abstract»

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  • Factor analysis for the quantification of renal cortical blood flow using O-15 water dynamic PET

    Publication Year: 2000 , Page(s): 18/153 - 18/156 vol.3
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    The renal cortical blood flow is an important index for the estimation of kidney function. Positron emission tomography (PET) allows noninvasive and quantitative estimate of blood flow. We applied factor analysis to O-15 water dynamic renal PET images to extract pure arterial and renal cortical time activity curves (TACs) for the estimation of renal cortical blood flow. Microsphere experiment was also performed to validate the renal cortical blood flow by factor analysis. In all the cases, factor images and their TACs could be extracted successfully. Input function by factor analysis and by arterial blood sampling was nearly same, except for the delay and dispersion. The renal cortical blood flow by factor analysis was within normal range (1.23-2.46 ml/min/g). In microsphere study, the flow by factor analysis was 2.49±0.47 ml/min/g and by microsphere was 2.52±0.19 ml/min/g View full abstract»

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  • Gamma-ray imaging with the laser-Compton-backscattered photons

    Publication Year: 2000 , Page(s): 23/65 - 23/67 vol.3
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    Gamma-ray imaging using quasi-monochromatic and energy-tunable photon beam was done. The photon was produced by the laser-Compton backscattering of 300-800 MeV electrons with laser photons. Images of a bulky material were obtained using 3 MeV and 20.7 MeV photons View full abstract»

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  • Imaging performances of the large area intra-operative camera POCI

    Publication Year: 2000
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    Summary form only received as follows: Intra-operative gamma imagers developed for small tumor localizations are of first interest for radio guided operative cancer surgery. In this context, the authors previously developed and evaluated a compact high resolution gamma imager POCI (Per Operative Compact Imager). This evaluation prototype has a 24 mm diameter field of view. The successful clinical evaluation of this device in theater block (sentinel node protocol for melanoma and breast cancers staging) led the authors to start the development a second prototype. Essentially, this device offers a larger sensitive area by coupling a 60 mm diameter head module (which associates crystal plate and a high resolution collimator) to a 40 mm diameter intensified position sensitive diode (IPSD). It has been designed in order to improve compactness and exploration efficiency during surgery. Measurements of basic detection parameters such as detection efficiency, spatial resolution, position linearity are reported. Characterization with phantoms are also presented and discussed View full abstract»

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  • Investigation of micro-columnar scintillators on an optical fiber coupled compact imaging system

    Publication Year: 2000 , Page(s): 21/19 - 21/23 vol.3
    Cited by:  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    A compact imaging system with a novel front-end detector is under investigation and development. Unique aspects of this collimator-less system include the use of many thousands of micro-columnar (<10 μm diameter) CsI front-end scintillators (140 and 200 microns tall on faceplates of plane glass, fiber optics (FO), and FO with statistical extramural absorbers (EMA)) that are coupled through a 4 times reducing FO bundle to a metal-channel multianode position sensitive photodetector. The highly discrete nature of the scintillator microcolumn arrays ensures very fine intrinsic spatial resolution, limited by the particle penetration and backscatter in the detector assembly, while their retro-reflector-tipped front-ends facilitate light propagation towards the photo-detector. Monte Carlo simulations confirmed the limiting nature of particle penetration on measurable resolution. With this system, absolute light output was highest for the taller arrays, which contradicts results of using much larger, quantized scintillators in other applications. While MTF measurements with an X-ray source indicate the best response with the arrays on FO+EMA substrates, measurements with high and medium (1.7 MeV and 635 keV) energy beta line sources yield the best responses with the plane glass substrate indicating that energy thresholding affects resolution in the classical way, even with these highly miniaturized arrays. Further experiments of complex positron emission distributions along with large gamma ray backgrounds yield images with minimal background contamination and no distortions View full abstract»

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  • A Monte Carlo study of high resolution PET with granulated dual layer detectors

    Publication Year: 2000 , Page(s): 20/11 - 20/15 vol.3
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    New arrays of Avalanche Photodiodes (APD) allow the design of novel highly granulated detector modules. Monte Carlo simulations were used to evaluate to what extent this feature can be used for high resolution, high sensitivity PET. Based on a fixed crystal front face of 2 mm2 and a fixed number of crystals, sensitivity and scatter fraction for three different geometries were determined: (a) Ring with 143 mm diameter; (b) Ring with only 71 mm diameter but double the axial extent (37 mm); (c) Ring with 71 mm diameter and two radial crystal layers. The sensitivity (a:b:c) was 0.3%:1.1%:1.5% for a line source in air. Studies using a simple mouse-like phantom showed the highest scatter fraction for (b) and comparable sensitivities for (b) and (c). The large diameter of (a) reduced the scatter fraction at the expenses of high sensitivity losses. Line source simulations showed a resolution of about 1.6 mm for (c) at the center for the field of view (FOV). Within a region of 20 mm within the FOV, the resolution of (c) remained close to 2 mm. Geometry (c) is being implemented in the new tomograph MADPET View full abstract»

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