ABSTRACT Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedi... more ABSTRACT Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedicated solely to X-Ray Computed Microtomography (XCMT). This is a third-generation instrument capable of producing tomographic volumes of 1-2 micron resolution over a 2-3mm field of view. Recent enhancements will be discussed. These have focussed on two issues: the desire for real-time data acquisition and processing and the need for highly monochromatic beam (.1 % energy bandpass). The latter will permit k-edge subtraction studies and will provide improved image contrast from below the Cr (6 keV) up to the Cs (36 keV) k-edge. A range of applications that benefit from these improvements will be discussed as well. These two goals are somewhat counterproductive, however; higher monochromaticity yields a lower flux forcing longer data acquisition times. To balance the two, a more efficient scintillator for X-ray conversion is being developed. Some testing of a prototype scintillator has been performed; ...
ABSTRACT X-ray phase-contrast imaging (XPCI) holds great promise for medical X-ray imaging with h... more ABSTRACT X-ray phase-contrast imaging (XPCI) holds great promise for medical X-ray imaging with high soft-tissue contrast. Obviating optical elements in the imaging chain, propagation-based XPCI (PB-XPCI) has definite advantages over other XPCI techniques in terms of cost, alignment and scalability. However, it imposes strict requirements on the spatial coherence of the source and the resolution of the detector. In this study, we demonstrate that using a coded X-ray source and sparsity-based reconstruction, we can significantly relax these requirements. Using numerical simulation, we assess the feasibility of our approach and study the effect of system parameters on the reconstructed image. The results are demonstrated with images obtained using a bench-top micro-focus XPCI system.
Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedicated sol... more Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedicated solely to X-Ray Computed Microtomography (XCMT). This is a third-generation instrument capable of producing tomographic volumes of 1 - 2 micron resolution over a 2 - 3 mm field of view. ...
In semiconductor crystal growth processes, the quality of the final product strongly depends on a... more In semiconductor crystal growth processes, the quality of the final product strongly depends on adequate control of freezing parameters including rate of solidification, the position and shape of the liquid-solid interface, and the temperature gradient at the interface. In particular, the shape and position of the interface directly affects material properties and must be controlled to a particular geometry to prevent loss of crystallinity and the formation of defects like spurious nucleation and twinning. The interface shape also affects stress in the crystals and can help prevent the resolidified material from sticking to the ampoule.
1999 IEEE Nuclear Science Symposium. Conference Record. 1999 Nuclear Science Symposium and Medical Imaging Conference (Cat. No.99CH37019), 1999
The authors have recently developed a digital X-ray imaging system based on a high resolution sci... more The authors have recently developed a digital X-ray imaging system based on a high resolution scintillator screen optically coupled to a specially designed large area CCD for use in mammographic procedures. The CCD consists of a 7 K×4 K array of 12 μm pixels, measuring 88.2 mm×51 mm and operated at room temperature, cooled only by ambient air circulation. With
ABSTRACT Adhesive bonded composites used in naval, aerospace, and automotive technologies require... more ABSTRACT Adhesive bonded composites used in naval, aerospace, and automotive technologies require routine nondestructive testing (NDT) to detect flaws and other integrity-reducing anomalies such as porosity, kissing disbonds, and delaminations. We have developed an x-ray radiography/CT system with fast scanning times based on high resolution, high efficiency scintillators coupled to a 1024 x 1024 pixel CCD via a fiberoptic taper. Typical CT systems for NDT use a fan beam x-ray source and a linear array of detectors, with scan times on the order of 10 hours depending on the desired resolution. The prototype CCD-based volumetric imaging system described here is capable of reducing this scan time to less than 1 hour while significantly improving resolution. Additionally, the system is capable of both CT and standard radiographic imaging. We have integrated two different scintillators in the prototype system. One is a structured CsI(Tl) screen, and the other is a new, pixelated, transparent optical ceramic (TOC) scintillator. This unique TOC has a density of 9.5 g/cm3 and a peak emission of 610 nm, particularly suitable for Si readouts. We present here the system design and preliminary results of radiographic imaging and volumetric CT reconstruction.
The performance of a new thin-film Lu2 O3 :Eu scintillator for single-cell radionuclide imaging i... more The performance of a new thin-film Lu2 O3 :Eu scintillator for single-cell radionuclide imaging is investigated. Imaging the metabolic properties of heterogeneous cell populations in real time is an important challenge with clinical implications. An innovative technique called radioluminescence microscopy has been developed to quantitatively and sensitively measure radionuclide uptake in single cells. The most important component of this technique is the scintillator, which converts the energy released during radioactive decay into luminescent signals. The sensitivity and spatial resolution of the imaging system depend critically on the characteristics of the scintillator, that is, the material used and its geometrical configuration. Scintillators fabricated using conventional methods are relatively thick and therefore do not provide optimal spatial resolution. A thin-film Lu2 O3 :Eu scintillator is compared to a conventional 500 μm thick CdWO4 scintillator for radioluminescence ima...
Medical Imaging 2011: Physics of Medical Imaging, 2011
Oxygen doped zinc telluride is a bright scintillator with one of the highest X-ray conversion eff... more Oxygen doped zinc telluride is a bright scintillator with one of the highest X-ray conversion efficiencies. These properties make it an ideal choice for wide range of X-ray imaging applications in biology and medicine. With an emission wavelength of 680 nm it is ideally suited for use with silicon imagers such as CCDs. In this paper we report a new
Abstract-- At RMD we have developed a detector for near simultaneous, combined, small animal SPEC... more Abstract-- At RMD we have developed a detector for near simultaneous, combined, small animal SPECT/CT imaging using a customized electron multiplying CCD (EMCCD) camera. The detector is based on a back-thinned EMCCD coupled to a high resolution CsI(Tl) scintillator via a ...
IEEE Nuclear Science Symposuim & Medical Imaging Conference, 2010
We report on the development of a novel scintillator in which the decay time of its light emissio... more We report on the development of a novel scintillator in which the decay time of its light emission varies continuously with the depth of an interaction in the crystal. The depth-of-interaction (DOI) information is thus encoded in the signal timing, which can be used to localize the position of the gamma interaction within the scintillator with high accuracy. This concept
Medical Applications of Radiation Detectors IV, 2014
A 1650 μm thick columnar CsI(Tl) scintillator for upgrading iQID detectors, which is a high-resol... more A 1650 μm thick columnar CsI(Tl) scintillator for upgrading iQID detectors, which is a high-resolution photon-counting gamma-ray and x-ray detector recently developed at the Center for Gamma-Ray Imaging (CGRI), has been studied in terms of sensitivity, spatial resolution and depth-of-interaction effects. To facilitate these studies, a new frame-parsing algorithm for processing raw event data is also proposed that has more degrees of freedom in data processing and can discriminate against a special kind of noise present in some low-cost intensifiers. The results show that in comparison with a 450 μm-thickness columnar CsI(Tl) scintillator, the 1650 μm thick CsI(Tl) scintillator provides more than twice the sensitivity at the expense of some spatial resolution degradation. The depth-of-interaction study also shows that event size and amplitude vary with scintillator thickness, which can assist in future detector simulations and 3D-interaction-position estimation.
ABSTRACT We present in this article the development of a photon-counting, energy-discriminating m... more ABSTRACT We present in this article the development of a photon-counting, energy-discriminating modular detector based on a pixelated CdZnTe sensor coupled pixel-by-pixel to a novel Digital Pixel Sensor (DPS) readout. The detector is designed for munitions inspection, breast X-ray CT and SPECT/MRI. The current DPS design can also be used to read out other solid-state sensors. The prototype detector is 5.5mm×5.5mm in size, and consists of 19×19 pixels on a 250μm pitch. The DPS is designed in a 0.35μm process, and every pixel includes a preamplifier, a leakage-current subtraction circuit, an auto-zeroed programmable-gain stage, five comparators, a variable-delay reset circuit and five 16bit counters. The module is expected to operate at high X-ray fluence exceeding 80MHz/mm2, and to improve resolution and contrast in images, while significantly enhancing their signal-to-noise ratio, and assist in identifying material composition via dual-energy imaging. The detector design, fabrication and anticipated performance are discussed.
Real-time, position sensitive detectors for X-rays and γ-rays are of increasing importance in num... more Real-time, position sensitive detectors for X-rays and γ-rays are of increasing importance in numerous medical and industrial areas. An important application of high energy X-rays is for dense-object radiography where high quality images of large volume objects have to be acquired in short time intervals. When compared to semiconductor detectors and Anger cameras, scintillators can be grown very thick enabling detection of high energy X-rays and γ-rays. As compared to single crystal scintillators, segmented scintillators have several potential advantages. Segmented scintillators allow smaller pixel size and have the potential to optimize the stopping power and spatial resolution, all of which are required for imaging high energy X-rays. We have developed a new approach to fabricate thick segmented scintillators with small pixel size using an injection process into a metal matrix to produce high stopping power and spatial resolution. This resulted in an increased light output (48% as...
Most currently available X-ray or gamma ray imaging detectors are based on energy integration ove... more Most currently available X-ray or gamma ray imaging detectors are based on energy integration over a certain period of time. We have been developing X-ray and gamma ray detectors based on the photon counting (with energy determination) concept using both direct and indirect radiation conversion, together with associated application-specific integrated circuits (ASICs). As an alternative to our ASIC design approach, we are also exploiting the potential of state-of-the-art silicon photomultipliers (SiPMs) and discrete electronics. In this paper we discuss the advantages and disadvantages of these two approaches and we report our latest results on our ASIC design efforts and our achievements on SiPM/CsI:Tl detector configurations. We will also discuss the potential uses and advantages that each offers to applications in medicine, imaging, homeland security and industry.
2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009
Abstract Advances in radiopharmaceuticals and clinical understanding have escalated the use of ... more Abstract Advances in radiopharmaceuticals and clinical understanding have escalated the use of intraoperative gamma probes in surgery, providing benefits that include increased specificity in tissue obtained for biopsy, minimally accessed incisions, and the reduction of inpatient ...
ABSTRACT Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedi... more ABSTRACT Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedicated solely to X-Ray Computed Microtomography (XCMT). This is a third-generation instrument capable of producing tomographic volumes of 1-2 micron resolution over a 2-3mm field of view. Recent enhancements will be discussed. These have focussed on two issues: the desire for real-time data acquisition and processing and the need for highly monochromatic beam (.1 % energy bandpass). The latter will permit k-edge subtraction studies and will provide improved image contrast from below the Cr (6 keV) up to the Cs (36 keV) k-edge. A range of applications that benefit from these improvements will be discussed as well. These two goals are somewhat counterproductive, however; higher monochromaticity yields a lower flux forcing longer data acquisition times. To balance the two, a more efficient scintillator for X-ray conversion is being developed. Some testing of a prototype scintillator has been performed; ...
ABSTRACT X-ray phase-contrast imaging (XPCI) holds great promise for medical X-ray imaging with h... more ABSTRACT X-ray phase-contrast imaging (XPCI) holds great promise for medical X-ray imaging with high soft-tissue contrast. Obviating optical elements in the imaging chain, propagation-based XPCI (PB-XPCI) has definite advantages over other XPCI techniques in terms of cost, alignment and scalability. However, it imposes strict requirements on the spatial coherence of the source and the resolution of the detector. In this study, we demonstrate that using a coded X-ray source and sparsity-based reconstruction, we can significantly relax these requirements. Using numerical simulation, we assess the feasibility of our approach and study the effect of system parameters on the reconstructed image. The results are demonstrated with images obtained using a bench-top micro-focus XPCI system.
Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedicated sol... more Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedicated solely to X-Ray Computed Microtomography (XCMT). This is a third-generation instrument capable of producing tomographic volumes of 1 - 2 micron resolution over a 2 - 3 mm field of view. ...
In semiconductor crystal growth processes, the quality of the final product strongly depends on a... more In semiconductor crystal growth processes, the quality of the final product strongly depends on adequate control of freezing parameters including rate of solidification, the position and shape of the liquid-solid interface, and the temperature gradient at the interface. In particular, the shape and position of the interface directly affects material properties and must be controlled to a particular geometry to prevent loss of crystallinity and the formation of defects like spurious nucleation and twinning. The interface shape also affects stress in the crystals and can help prevent the resolidified material from sticking to the ampoule.
1999 IEEE Nuclear Science Symposium. Conference Record. 1999 Nuclear Science Symposium and Medical Imaging Conference (Cat. No.99CH37019), 1999
The authors have recently developed a digital X-ray imaging system based on a high resolution sci... more The authors have recently developed a digital X-ray imaging system based on a high resolution scintillator screen optically coupled to a specially designed large area CCD for use in mammographic procedures. The CCD consists of a 7 K×4 K array of 12 μm pixels, measuring 88.2 mm×51 mm and operated at room temperature, cooled only by ambient air circulation. With
ABSTRACT Adhesive bonded composites used in naval, aerospace, and automotive technologies require... more ABSTRACT Adhesive bonded composites used in naval, aerospace, and automotive technologies require routine nondestructive testing (NDT) to detect flaws and other integrity-reducing anomalies such as porosity, kissing disbonds, and delaminations. We have developed an x-ray radiography/CT system with fast scanning times based on high resolution, high efficiency scintillators coupled to a 1024 x 1024 pixel CCD via a fiberoptic taper. Typical CT systems for NDT use a fan beam x-ray source and a linear array of detectors, with scan times on the order of 10 hours depending on the desired resolution. The prototype CCD-based volumetric imaging system described here is capable of reducing this scan time to less than 1 hour while significantly improving resolution. Additionally, the system is capable of both CT and standard radiographic imaging. We have integrated two different scintillators in the prototype system. One is a structured CsI(Tl) screen, and the other is a new, pixelated, transparent optical ceramic (TOC) scintillator. This unique TOC has a density of 9.5 g/cm3 and a peak emission of 610 nm, particularly suitable for Si readouts. We present here the system design and preliminary results of radiographic imaging and volumetric CT reconstruction.
The performance of a new thin-film Lu2 O3 :Eu scintillator for single-cell radionuclide imaging i... more The performance of a new thin-film Lu2 O3 :Eu scintillator for single-cell radionuclide imaging is investigated. Imaging the metabolic properties of heterogeneous cell populations in real time is an important challenge with clinical implications. An innovative technique called radioluminescence microscopy has been developed to quantitatively and sensitively measure radionuclide uptake in single cells. The most important component of this technique is the scintillator, which converts the energy released during radioactive decay into luminescent signals. The sensitivity and spatial resolution of the imaging system depend critically on the characteristics of the scintillator, that is, the material used and its geometrical configuration. Scintillators fabricated using conventional methods are relatively thick and therefore do not provide optimal spatial resolution. A thin-film Lu2 O3 :Eu scintillator is compared to a conventional 500 μm thick CdWO4 scintillator for radioluminescence ima...
Medical Imaging 2011: Physics of Medical Imaging, 2011
Oxygen doped zinc telluride is a bright scintillator with one of the highest X-ray conversion eff... more Oxygen doped zinc telluride is a bright scintillator with one of the highest X-ray conversion efficiencies. These properties make it an ideal choice for wide range of X-ray imaging applications in biology and medicine. With an emission wavelength of 680 nm it is ideally suited for use with silicon imagers such as CCDs. In this paper we report a new
Abstract-- At RMD we have developed a detector for near simultaneous, combined, small animal SPEC... more Abstract-- At RMD we have developed a detector for near simultaneous, combined, small animal SPECT/CT imaging using a customized electron multiplying CCD (EMCCD) camera. The detector is based on a back-thinned EMCCD coupled to a high resolution CsI(Tl) scintillator via a ...
IEEE Nuclear Science Symposuim & Medical Imaging Conference, 2010
We report on the development of a novel scintillator in which the decay time of its light emissio... more We report on the development of a novel scintillator in which the decay time of its light emission varies continuously with the depth of an interaction in the crystal. The depth-of-interaction (DOI) information is thus encoded in the signal timing, which can be used to localize the position of the gamma interaction within the scintillator with high accuracy. This concept
Medical Applications of Radiation Detectors IV, 2014
A 1650 μm thick columnar CsI(Tl) scintillator for upgrading iQID detectors, which is a high-resol... more A 1650 μm thick columnar CsI(Tl) scintillator for upgrading iQID detectors, which is a high-resolution photon-counting gamma-ray and x-ray detector recently developed at the Center for Gamma-Ray Imaging (CGRI), has been studied in terms of sensitivity, spatial resolution and depth-of-interaction effects. To facilitate these studies, a new frame-parsing algorithm for processing raw event data is also proposed that has more degrees of freedom in data processing and can discriminate against a special kind of noise present in some low-cost intensifiers. The results show that in comparison with a 450 μm-thickness columnar CsI(Tl) scintillator, the 1650 μm thick CsI(Tl) scintillator provides more than twice the sensitivity at the expense of some spatial resolution degradation. The depth-of-interaction study also shows that event size and amplitude vary with scintillator thickness, which can assist in future detector simulations and 3D-interaction-position estimation.
ABSTRACT We present in this article the development of a photon-counting, energy-discriminating m... more ABSTRACT We present in this article the development of a photon-counting, energy-discriminating modular detector based on a pixelated CdZnTe sensor coupled pixel-by-pixel to a novel Digital Pixel Sensor (DPS) readout. The detector is designed for munitions inspection, breast X-ray CT and SPECT/MRI. The current DPS design can also be used to read out other solid-state sensors. The prototype detector is 5.5mm×5.5mm in size, and consists of 19×19 pixels on a 250μm pitch. The DPS is designed in a 0.35μm process, and every pixel includes a preamplifier, a leakage-current subtraction circuit, an auto-zeroed programmable-gain stage, five comparators, a variable-delay reset circuit and five 16bit counters. The module is expected to operate at high X-ray fluence exceeding 80MHz/mm2, and to improve resolution and contrast in images, while significantly enhancing their signal-to-noise ratio, and assist in identifying material composition via dual-energy imaging. The detector design, fabrication and anticipated performance are discussed.
Real-time, position sensitive detectors for X-rays and γ-rays are of increasing importance in num... more Real-time, position sensitive detectors for X-rays and γ-rays are of increasing importance in numerous medical and industrial areas. An important application of high energy X-rays is for dense-object radiography where high quality images of large volume objects have to be acquired in short time intervals. When compared to semiconductor detectors and Anger cameras, scintillators can be grown very thick enabling detection of high energy X-rays and γ-rays. As compared to single crystal scintillators, segmented scintillators have several potential advantages. Segmented scintillators allow smaller pixel size and have the potential to optimize the stopping power and spatial resolution, all of which are required for imaging high energy X-rays. We have developed a new approach to fabricate thick segmented scintillators with small pixel size using an injection process into a metal matrix to produce high stopping power and spatial resolution. This resulted in an increased light output (48% as...
Most currently available X-ray or gamma ray imaging detectors are based on energy integration ove... more Most currently available X-ray or gamma ray imaging detectors are based on energy integration over a certain period of time. We have been developing X-ray and gamma ray detectors based on the photon counting (with energy determination) concept using both direct and indirect radiation conversion, together with associated application-specific integrated circuits (ASICs). As an alternative to our ASIC design approach, we are also exploiting the potential of state-of-the-art silicon photomultipliers (SiPMs) and discrete electronics. In this paper we discuss the advantages and disadvantages of these two approaches and we report our latest results on our ASIC design efforts and our achievements on SiPM/CsI:Tl detector configurations. We will also discuss the potential uses and advantages that each offers to applications in medicine, imaging, homeland security and industry.
2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009
Abstract Advances in radiopharmaceuticals and clinical understanding have escalated the use of ... more Abstract Advances in radiopharmaceuticals and clinical understanding have escalated the use of intraoperative gamma probes in surgery, providing benefits that include increased specificity in tissue obtained for biopsy, minimally accessed incisions, and the reduction of inpatient ...
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