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Journal of Instrumentation 01/2013; 8. · 1.87 Impact Factor
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ABSTRACT: We present three new autoradiography methods to map positron emission rate of a bio-specimen slice with high resolution. One is based on LBNL scientific charge coupled device (CCD) and the other two are based on conventional CCDs. High conversion efficiency (100k e-h pairs / 0.5 MeV positron) and low dark current (1.75 × 10(-4) e-/pix/sec) can be achieved using the LBNL CCD. The theoretical calculations and preliminary experiments show that an 86 μm spatial resolution can be achieved when imaging a 100 μm thick tissue soaked with (18)F which produce higher energy positron. The main disadvantage of the LBNL CCD we tested is that a very low operating temperature is required to eliminate dark current. This dramatically increases the system cost. In addition, the integration time of the CCD needs to be short enough to avoid overlapping of the positron trajectories. Conventional CCDs have lower conversion efficiency (2k e-h pairs / 0.5 MeV positron) and higher dark current (200 e-/pix/sec), but are more cost-efficient and the requirement for the readout frequency is much lower. The conversion efficiency of the conventional CCD imager can be improved by 17 times by inserting a 100 μm layer of phosphor between the sample and the imager. However, the light emitted from the phosphor screen will be ~100 μm diameter, which severely degrades the spatial resolution. A high readout frequency is also required to avoid the overlapping. The CCD systems designed in this study will be used to map positron emission rate of bio-specimens such as cancerous tissues acquired in regular biopsy procedure. They can also be used to corroborate tracer kinetic modeling at a cellular level.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:6273-6.
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ABSTRACT: Multimodality imaging has an increasing role in the management of a large number of diseases, particularly if both functional and structural information are acquired and accurately registered. Transrectal ultrasound (TRUS) imaging is currently an integral part of prostate cancer diagnosis and treatment procedures, providing high-resolution anatomical detail of the prostate region. Positron Emission Tomography (PET) imaging with <sup>11</sup>C-choline is a sensitive functional imaging technique that can identify biochemical states associated with prostate cancer. We believe that merging these prostate imaging technologies will help identify the location and aggressiveness of prostate cancer. We envision using dual PET-TRUS prostate imaging to guide biopsy, guide treatment procedures, and detect local recurrence earlier than is currently possible. Hence, we have developed a dual PET-TRUS prostate imaging system and protocol designed to allow accurate 3-D image registration. We have evaluated this PET-TRUS system by performing dual PET-TRUS imaging of custom phantoms. We describe here our dual-modality imaging system, custom phantoms and phantom study results. We also discuss our investigation of the PET-TRUS registration accuracy. We measure an average PET-TRUS registration error for our phantom studies of 2.1 ±1.7 mm in the x direction, 1.9 ±1.6 mm in the y direction, and 0.6 ±0.2 mm in the z direction. This registration accuracy is sufficient for some clinical applications such as biopsy guidance and early detection of recurrence.
IEEE Transactions on Nuclear Science 07/2011; · 1.45 Impact Factor
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ABSTRACT: We present the design for OpenPET, an electronics readout system designed for prototype radiotracer imaging instruments. The critical requirements are that it has sufficient performance, channel count, channel density, and power consumption to service a complete camera, and yet be simple, flexible, and customizable enough to be used with almost any detector or camera design. An important feature of this system is that each analog input is processed independently. Each input can be configured to accept signals of either polarity as well as either differential or ground referenced signals. Each signal is digitized by a continuously sampled ADC, which is processed by an FPGA to extract pulse height information. A leading edge discriminator creates a timing edge that is “time stamped” by a TDC implemented inside the FPGA. This digital information from each channel is sent to an FPGA that services 16 analog channels, and information from multiple channels is processed by this FPGA to perform logic for crystal lookup, DOI calculation, calibration, etc. As all of this processing is controlled by firmware and software, it can be modified/customized easily. The system is open source, meaning that all technical data (specifications, schematics and board layout files, source code, and instructions) will be publicly available.
IEEE Transactions on Nuclear Science 11/2010; · 1.45 Impact Factor
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ABSTRACT: We have explored methods for optimizing the timing resolution of an LSO-based detector module for a single-ring, “demonstration” time-of-flight PET camera. By maximizing the area that couples the scintillator to the PMT and minimizing the average path length that the scintillation photons travel, a single detector timing resolution of 218 ps fwhm is measured, which is considerably better than the ~385 ps fwhm obtained by commercial LSO or LYSO TOF detector modules. We explored different surface treatments (saw-cut, mechanically polished, and chemically etched) and reflector materials (Teflon tape, ESR, Lumirror, Melinex, white epoxy, and white paint), and found that for our geometry, a chemically etched surface had 5% better timing resolution than the saw-cut or mechanically polished surfaces, and while there was little dependence on the timing resolution between the various reflectors, white paint and white epoxy were a few percent better. Adding co-dopants to LSO shortened the decay time from 40 ns to ~30 ns but maintained the same or higher total light output. This increased the initial photoelectron rate and so improved the timing resolution by 15%. Using photomultiplier tubes with higher quantum efficiency (blue sensitivity index of 13.5 rather than 12) improved the timing resolution by an additional 5%. By choosing the optimum surface treatment (chemically etched), reflector (white paint), LSO composition (co-doped), and PMT (13.5 blue sensitivity index), the coincidence timing resolution of our detector module was reduced from 309 ps to 220 ps fwhm.
IEEE Transactions on Nuclear Science 07/2010; · 1.45 Impact Factor
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ABSTRACT: To accurately predict the light collection from a scintillating crystal through Monte Carlo simulations, it is crucial to know the angular distribution from the surface reflectance. Current Monte Carlo codes allow the user to set the optical reflectance to a linear combination of backscatter spike, specular spike, specular lobe, and Lambertian reflections. However, not all light distributions can be expressed in this way. In addition, the user seldom has the detailed knowledge about the surfaces that is required for accurate modeling. We have previously measured the angular distributions within BGO crystals and now incorporate these data as look-up-tables (LUTs) into modified Geant4 and GATE Monte Carlo codes. The modified codes allow the user to specify the surface treatment (ground, etched, or polished), the attached reflector (Lumirror®, Teflon®, ESR film, Tyvek®, or TiO paint), and the bonding type (air-coupled or glued). Each LUT consists of measured angular distributions with 4 $^{circ}$ by 5 $^{circ}$ resolution in theta and phi, respectively, for incidence angles from 0 $^{circ}$ to 90 $^{circ}$ degrees, in 1 $^{circ}$ -steps. We compared the new codes to the original codes by running simulations with a $3times 10times 30 {rm mm}^{3}$ BGO crystal coupled to a PMT. The simulations were then compared to measurements. Light output was measured by counting the photons detected by the PMT with the 3 $times$ 10, 3 $time-
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s$ 30, or $10times 30 {rm mm}^{2}$ side coupled to the PMT, respectively. Our new code shows better agreement with the measured data than the current Geant4 code. The new code can also simulate reflector materials that are not pure specular or Lambertian reflectors, as was previously required. Our code is also more user friendly, as no detailed knowledge about the surfaces or light distributions is required from the user.
IEEE Transactions on Nuclear Science 07/2010; · 1.45 Impact Factor
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ABSTRACT: The scintillation properties of powders and single-crystals of BaFI doped with Eu<sup>2+</sup> are presented. Single crystals were grown by the vertical Bridgman technique. Under optical and X-ray excitation, the samples exhibit a narrow Eu<sup>2+</sup> 5d-4f transition emission centered at 405 nm. The scintillation light output is estimated to be 55 0005 000 photons/MeV at 662 keV with 85% of the light decaying within 600 ns. An energy resolution of 8.5% full width at half maximum (FWHM) has been achieved using this scintillator for 662 keV excitation (<sup>137</sup>Cs source) at room temperature.
IEEE Transactions on Nuclear Science 07/2010; · 1.45 Impact Factor
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ABSTRACT: A computer simulation study has been conducted to investigate the feasibility of a positron emission tomography (PET) detector design by using micro-channel plate (MCP) photomultiplier tubes (PMT) with transmission-line (TL) read-out and waveform sampling. The detector unit consisted of a 24×24 array of pixelated LSO crystals, each of which was 4×4×25 mm(3) in size, and two 102×102 mm(2) MCP-PMTs coupled to both sides of the scintillator array. The crystal (and TL) pitch was 4.25 mm and reflective medium was inserted between the crystals. The transport of the optical photons inside the scintillator were simulated by using the Geant4 package. The output pulses of the MCP-PMT/TL unit were formed by applying the measured single photo-electron response of the MCP-PMT/TL unit to each individual photon that interacts with the photo-cathode of the MCP-PMT. The waveforms of the pulses at both ends of the TL strips were measured and analyzed to produce energy and timing information for the detected event. An experimental setup was developed by employing a Photonis Planacon MCP-PMT (XP85022) and a prototype TL board for measuring the single photo-electron response of the MCP-PMT/TL. The simulation was validated by comparing the predicted output pulses to measurements obtained with a single MCP-PMT/TL coupled to an LSO crystal exposed to 511 keV gamma rays. The validated simulation was then used to investigate the performance of the proposed new detector design. Our simulation result indicates an energy resolution of ~11% at 511 keV. When using a 400-600 keV energy window, we obtain a coincidence timing resolution of ~323 ps FWHM and a coincidence detection efficiency of ~40% for normally-incident 511keV photons. For the positioning accuracy, it is determined by the pitch of the TLs (and crystals) in the direction normal to the TLs and measured to be ~2.5 mm in the direction parallel to the TLs. The energy and timing obtained at the front- and back-end of the scintillator array also show differences that are correlated with the depth of interaction of the event.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2010; 622(3):628-636. · 1.21 Impact Factor
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ABSTRACT: A computer simulation study has been conducted to investigate the design of a PET detector module. The detector unit consisted of a 24Ã24 array of pixelated LSO crystals, each was 4Ã4Ã25 mm<sup>3</sup> in size, and two 102Ã102 mm<sup>2</sup> microchannel plate (MCP) PMTs coupled to both sides of scintillators. The crystal pitch was 4.25 mm and reflective media was inserted between crystals. The signals from MCP were readout using a transmission-line scheme. The optical photon inside scintillator was simulated by using the Geant4 package and the output signals of the MCP was formed by applying the electrical responses measured of the MCP to each individual detected photon. A experimental setup was built using a Photonis planacon MCP(XP85022) and a Transmission line board to measure the characteristics of MCP/TL. The measured single photoelectron response(SER) was fed to the simulation of the electrical signal. The responses to 511 keV gamma of the test setup were compared to the simulation results for the validation. The simulation study results showed an energy resolution of ~11% at 511 keV for the detector module. When using a 400-600 keV energy window, we obtained a coincidence timing resolution of ~323 ps FWHM and a coincidence detection efficiency of ~40% for normally incident 511 keV photons. The position resolution was measured to be ~4.25 mm. The readout at both ends of scintillator made it possible to infer depth of interaction(DOI) based on the energy asymmetry and time differences. The simulation study showed that the design is suitable for Time of Flight(TOF) PET with DOI capability.
Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
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ABSTRACT: We present the design for OpenPET, an electronics readout system designed for prototype radiotracer imaging instruments. The critical requirements are that it have sufficient performance, channel count, channel density, and power consumption to service a complete camera, and yet be simple, flexible, and customizable enough to be used with almost any detector or camera design. A unique feature of this system is that each analog input is processed independently. Each input can be configured to accept signals of either polarity as well as either differential or ground referenced signals. Each signal is digitized by a continuously sampled ADC, which is processed by an FPGA to extract pulse height information. A leading edge discriminator creates a timing edge that is ¿time stamped¿ by a TDC implemented inside the FPGA. This digital information from each channel is sent to an FPGA that services 16 analog channels, and information from multiple channels is processed by this FPGA to perform logic for crystal lookup, DOI calculation, calibration, etc. As this processing is software controlled, it can be modified / customized easily. The system is be open source, meaning that all technical data (specifications, schematics and board layout files, source code, and instructions) will be publicly available.
Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
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ABSTRACT: Radionuclide techniques will be increasingly important for the development of biofuels, since they can both uniquely characterize metabolic pathways and image large model systems. We are investigating the application of nuclear medical imaging tools and techniques to biofuel development, using high-sensitivity chromatographic radiation detectors and compounds radiolabeled with short-lived, cyclotron-produced, positron-emitting isotopes (e.g., <sup>11</sup>C). The application of high-sensitivity radiation detectors to standard chromatographic techniques should allow for the measurement of numerous pathway constituents whose levels normally fall below detection limits of conventional instrumentation. In this paper, we describe a proposed parallel-plane PET camera designed for HPLC (high performance liquid chromatography) with over 40 times greater sensitivity than a conventional HPLC radiation detector; this PET camera could be used to image radioactivity in the HPLC exit tube or column. We also present results using a high-sensitivity HPLC radiation detector comprised of 8 HR+ PET detector modules arranged into a parallel plane and read out with HRRT electronics. This high-sensitivity radiation detector was placed in line after a conventional HPLC radiation detector (a small CsI:Tl scintillator crystal coupled to a PIN photodiode). If we inject 9.3 ¿Ci of [<sup>18</sup>F]FDG into the HPLC system, we see similarly shaped peaks with an excellent signal-to-noise ratio from both radiation detectors. If we inject only 4.1 nCi of [<sup>18</sup>F]FDG, we measure a signal-to-noise ratio of 27:1 with the high-sensitivity radiation detector and about 3:1 for the conventional radiation detector. We have therefore demonstrated that a high-sensitivity radiation detector, using a parallel-plane PET camera, could become an important tool for fundamental biofuel research.
Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
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ABSTRACT: A PET detector design using the continuous scintillator slab was investigated. The detector unit consists of two layers of LSO scintillator slab, each slab size of 102Ã102Ã5mm<sup>3</sup>, and two large area microchannel plate (MCP) PMTs, 102Ã102mm<sup>2</sup>, coupled to scintillator slabs. The optical photon inside scintillator was simulated using Geant4 package and the electrical signal of MCP was formed using the measured characteristics of MCP and Geant4 output. The signals from MCP were readout using the transmission line (TL) scheme with 4.25mm pitch. The multi-layers of structure enable us to extract the depth of interaction in addition to position, energy and timing in an event. The detector response was measured by impinging the pair of 511keV gamma upon the detector. As preliminary results, we obtained ~12% (FWHM) of energy resolution at 511keV and ~360ps (FWHM) coincidence timing resolution while keeping 14% detection efficiency at 511keV. The position resolution was measured ~2.3mm (RMS) at the center. Due to its simplified structure, the detector can be easily extendable to several layers of slab to increase the sensitivity. The fast timing characteristics of MCP combined with the high sensitivity of LSO makes this design reliable for TOF PET application.
Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
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ABSTRACT: We demonstrate an alternate application of high-sensitivity radiotracer imaging technologies developed for nuclear medical imaging. There are several available radioisotopes, namely <sup>51</sup>Cr and <sup>99m</sup>Tc, that are particularly appealing for studying environmental remediation techniques, notably for modeling toxic element runoff through the soil near former nuclear facilities such as the Hanford reactors in Washington state (USA). <sup>52</sup>Cr (stable) and <sup>99</sup>Tc (2.3?10<sup>6</sup> year half-life) are important reactor-generated contaminants that have entered the groundwater. There are numerous studies being conducted to model transport of these compounds in different types of soil such as sand, clay, dirt and gravel. The speed and character of contaminant transport through medium depends on chemical composition of the particles, chemical composition of water, physical properties of the medium (particle size, homogeneity, temperature) and on content of different types of microorganisms. Measurements are typically performed by flowing water containing <sup>52</sup>Cr or <sup>99</sup>Tc through sediment columns (tubes a few cm in diameter and 0.5-1 meter long) and monitoring the in-and out- flows of contaminants. We will support the effort to develop different methods of reducing the contaminant transport speed by using SPECT imaging to study transport of the singlephoton emitting surrogates <sup>51</sup>Cr and <sup>99m</sup>Tc. By quantitatively imaging the contaminant distribution in the sediment column as a function of time, a much richer set of data can be obtained. We will compare contaminant transport in various media under different conditions including standard diffusion and flow at different speeds and volumes. Experimental work will be supplemented with theoretical analysis and modeling of transport processes, including studies of diffusion and chemical exchange using a standard multi-compartment model. In this conference record, w-
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e present the results of two studies of technetium 99m transport in hydrated sand, including both planar and tomographic SPECT images of the columns acquired at different conditions.
Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
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ABSTRACT: Multi-modality imaging has an increasing role in the diagnosis and treatment of a large number of diseases, particularly if both functional and anatomical information are acquired and accurately co-registered. Hence, there is a resulting need for multi-modality phantoms in order to validate image co-registration and calibrate the imaging systems. We present our PET-ultrasound phantom development, including PET and ultrasound images of a simple prostate phantom. We use agar and gelatin mixed with a radioactive solution. We also present our development of custom multi-modality phantoms that are compatible with PET, transrectal ultrasound (TRUS), MRI and CT imaging. We describe both our selection of tissue mimicking materials and phantom construction procedures. These custom PET-TRUS-CT-MRI prostate phantoms use agar-gelatin radioactive mixtures with additional contrast agents and preservatives. We show multi-modality images of these custom prostate phantoms, as well as discuss phantom construction alternatives. Although we are currently focused on prostate imaging, this phantom development is applicable to many multi-modality imaging applications.
IEEE Transactions on Nuclear Science 11/2009; · 1.45 Impact Factor
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ABSTRACT: We present the design for OpenPET, an electronics readout system designed for prototype radiotracer imaging instruments. The critical requirements are that it has sufficient performance, channel count, channel density, and power consumption to service a complete camera, and yet be simple, flexible, and customizable enough to be used with almost any detector or camera design. An important feature of this system is that each analog input is processed independently. Each input can be configured to accept signals of either polarity as well as either differential or ground referenced signals. Each signal is digitized by a continuously sampled ADC, which is processed by an FPGA to extract pulse height information. A leading edge discriminator creates a timing edge that is "time stamped" by a TDC implemented inside the FPGA. This digital information from each channel is sent to an FPGA that services 16 analog channels, and information from multiple channels is processed by this FPGA to perform logic for crystal lookup, DOI calculation, calibration, etc. As all of this processing is controlled by firmware and software, it can be modified / customized easily. The system is open source, meaning that all technical data (specifications, schematics and board layout files, source code, and instructions) will be publicly available.
IEEE Transactions on Nuclear Science 10/2009; 2009:3491-3495. · 1.45 Impact Factor
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ABSTRACT: On the basis of nonproportionality data obtained for several scintillators, we have developed a model to describe the carrier dynamics to fit the light yield versus electron energy. The theory of Onsager was adapted to explain how the carriers form excitons or sequentially arrive at the activators to promote the ion to an excited state, and the theory of Birks was employed to allow for exciton-exciton annihilation. We then developed a second model to deduce the degradation in resolution that results from nonproportionality by evoking Landau fluctuations, which are essentially variations in the deposited energy density that occur as the high energy electron travels along its trajectory. In general there is agreement with the data, in terms of fitting the nonproportionality curves and reproducing the literature values of nonproportionality's contribution to the scintillator resolution.
IEEE Transactions on Nuclear Science 09/2009; · 1.45 Impact Factor
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ABSTRACT: We present a model to describe the origin of non-proportional dependence of scintillator light yield on the energy of an ionizing particle. The non-proportionality is discussed in terms of energy relaxation channels and their linear and non-linear dependences on the deposited energy. In this approach, the scintillation response is described as a function of the deposited energy deposition and the kinetic rates of each relaxation channel. This mathematical framework allows both a qualitative interpretation and a quantitative fitting representation of scintillation non-proportionality response as function of kinetic rates. This method was successfully applied to thallium doped sodium iodide measured with SLYNCI, a new facility using the Compton coincidence technique. Finally, attention is given to the physical meaning of the dominant relaxation channels, and to the potential causes responsible for the scintillation non-proportionality. We find that thallium doped sodium iodide behaves as if non-proportionality is due to competition between radiative recombinations and non-radiative Auger processes.
IEEE Transactions on Nuclear Science 09/2009; · 1.45 Impact Factor
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ABSTRACT: Single crystals of SrI<sub>2</sub>:Eu and SrI<sub>2</sub>:Ce/Na were grown from anhydrous iodides by the vertical Bridgman technique in evacuated silica ampoules. Growth rates were of the order of 5-30 mm/day. Radioluminescence spectra of SrI<sub>2</sub>:Eu and SrI<sub>2</sub>:Ce/Na exhibit a broad band due to Eu<sup>2+</sup> and Ce<sup>3+</sup> emission, respectively. The maximum in the luminescence spectrum of SrI<sub>2</sub>:Eu is found at 435 nm. The spectrum of SrI<sub>2</sub>:Ce/Na exhibits a doublet peaking at 404 and 435 nm attributed to Ce<sup>3+</sup> emission, while additional impurity-or defect-related emission is present at approximately 525 nm. The strontium iodide scintillators show very high light yields of up to 120 000 photons/MeV, have energy resolutions down to 3% at 662 keV (Full Width Half Maximum) and exhibit excellent light yield proportionality with a standard deviation of less than 5% between 6 and 460 keV.
IEEE Transactions on Nuclear Science 07/2009; · 1.45 Impact Factor
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N.J. Cherepy,
S.A. Payne,
S.J. Asztalos,
G. Hull,
J.D. Kuntz,
T. Niedermayr,
S. Pimputkar,
J.J. Roberts,
R.D. Sanner,
T.M. Tillotson,
E. van Loef,
C.M. Wilson,
K.S. Shah,
U.N. Roy,
R. Hawrami,
A. Burger,
L.A. Boatner,
Woon-Seng Choong, W.W. Moses
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ABSTRACT: New scintillators for high-resolution gamma ray spectroscopy have been identified, grown and characterized. Our development efforts have focused on two classes of high-light-yield materials: europium-doped alkaline earth halides and cerium-doped garnets. Of the halide single crystals we have grown by the Bridgman method-SrI<sub>2</sub>, CaI<sub>2</sub>, SrBr<sub>2</sub>, BaI<sub>2</sub> and BaBr<sub>2</sub>-SrI<sub>2</sub> is the most promising. SrI<sub>2</sub>(Eu) emits into the Eu<sup>2+</sup> band, centered at 435 nm, with a decay time of 1.2 mus and a light yield of up to 115,000 photons/MeV. It offers energy resolution better than 3% FWHM at 662 keV, and exhibits excellent light yield proportionality. Transparent ceramic fabrication allows the production of gadolinium- and terbium-based garnets which are not growable by melt techniques due to phase instabilities. The scintillation light yields of cerium-doped ceramic garnets are high, 20,000-100,000 photons/MeV. We are developing an understanding of the mechanisms underlying energy dependent scintillation light yield non-proportionality and how it affects energy resolution. We have also identified aspects of optical design that can be optimized to enhance the energy resolution.
IEEE Transactions on Nuclear Science 07/2009; · 1.45 Impact Factor
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ABSTRACT: As an approach to realizing all-digital data acquisition for positron emission tomography (PET), we have previously proposed and studied a multi-threshold sampling method to generate samples of a PET event waveform with respect to a few user-defined amplitudes. In this sampling scheme, one can extract both the energy and timing information for an event. In this paper, we report our prototype implementation of this sampling method and the performance results obtained with this prototype. The prototype consists of two multi-threshold discriminator boards and a time-to-digital converter (TDC) board. Each of the multi-threshold discriminator boards takes one input and provides up to 8 threshold levels, which can be defined by users, for sampling the input signal. The TDC board employs the CERN HPTDC chip that determines the digitized times of the leading and falling edges of the discriminator output pulses. We connect our prototype electronics to the outputs of two Hamamatsu R9800 photomultiplier tubes (PMTs) that are individually coupled to a 6.25×6.25×25mm(3) LSO crystal. By analyzing waveform samples generated by using four thresholds, we obtain a coincidence timing resolution of about 340 ps and an ∼18% energy resolution at 511 keV. We are also able to estimate the decay-time constant from the resulting samples and obtain a mean value of 44ns with an ∼9 ns FWHM. In comparison, using digitized waveforms obtained at a 20 GSps sampling rate for the same LSO/PMT modules we obtain ∼300 ps coincidence timing resolution, ∼14% energy resolution at 511 keV, and ∼5 ns FWHM for the estimated decay-time constant. Details of the results on the timing and energy resolutions by using the multi-threshold method indicate that it is a promising approach for implementing digital PET data acquisition.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 05/2009; 602(2):618-621. · 1.21 Impact Factor
