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Novel method to measure the intrinsic spatial resolution in PET detectors based on monolithic crystals
摘要： The main aim of this work is to provide a method to retrieve the intrinsic spatial resolution of a gamma-ray detector block based on monolithic crystals within an assembled scanner. This method consists on a discrimination of the data using a software collimation process. The results are compared with an alternative method of separating two detector blocks far enough to produce a "virtual" source collimation due to the geometric constraints on the allowed coincidence event angles. A theoretical model has been deduced to fit the measured light distribution profiles, allowing estimating the detector intrinsic spatial resolution. The detector intrinsic spatial resolution is expected to follow a Gaussian distribution and the positron-emitter source shape, given the small size of a 22Na source with 0.25 mm in diameter, can be assumed to follow a Lorentzian profile. However, the collimation of the data modifies the source shape that is no longer a pure Lorentzian distribution. Therefore, the model is based on the convolution of a Gaussian shaped distribution (contribution of the detector) and a modified Lorentzian distribution (contribution of the collimated source profile) that takes into account the collimation effect. Three LYSO crystals geometries have been studied in the present work, namely a 10 mm thick trapezoidal monolithic block, and two rectangular monolithic blocks with thicknesses of 15 mm and 20 mm, respectively. All the blocks have size dimensions of 50 mm × 50 mm. The experimental results yielded an intrinsic detector spatial resolution of 0.64 ± 0.02 mm, 0.82 ± 0.02 and 1.07 ± 0.03 mm, for the 10 mm, 15 mm and 20 mm thick blocks, respectively, when the source was placed at the center of the detector. The detector intrinsic spatial resolution was moreover evaluated across one of the axis of each crystal. These values worsen to an average value of 0.68 ± 0.04 mm, 0.90 ± 0.14 and 1.29 ± 0.19 mm, respectively, when the whole crystal size is considered, as expected. These tests show an accurate method to determine the intrinsic spatial resolution of monolithic-based detector blocks, once assembled in the PET system.
关键词： Intrinsic spatial resolution,SiPM array,Monolithic blocks,Positron Emission Tomography,Gamma ray detectors
更新于2025-09-23 15:23:52
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Digital pulse timing with semiconductor gamma-ray detectors using a wavelet transform technique
摘要： Obtaining precise timing information from semiconductor gamma-ray detectors is of great interest for a variety of applications such as high-resolution positron emission tomography. However, pulse timing with these detectors through the common constant-fraction discrimination (CFD) method is strongly affected by the time-walk error that results from the inherent variations in the shape of the detectors’ pulses. This paper reports on the use of the wavelet transform for minimizing the time-walk error in digital CFD pulse timing with semiconductor gamma-ray detectors. The details of the method are described, and the experimental results with a 1 mm thick CdTe detector are shown. It is demonstrated that, by using the Haar wavelet transform of the digitized preampli?er pulses, the original tailed time spectrum of the detector with a time resolution of 8.22 ± 0.12 ns at full-width at half-maximum (FWHM) in the energy range of 300-550 keV improves to a symmetric time spectrum with a time resolution of 3.39 ± 0.02 ns (FWHM).
关键词： wavelet transform,time-walk error,CdTe detector,digital pulse timing,semiconductor gamma-ray detectors
更新于2025-09-23 15:21:21
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[IEEE 2020 International SAUPEC/RobMech/PRASA Conference - Cape Town, South Africa (2020.1.29-2020.1.31)] 2020 International SAUPEC/RobMech/PRASA Conference - Thin film photovoltaic module characterisation based in indoor and outdoor methods
摘要： This paper is the fifth in a series of articles on the basic physics of light yield nonproportionality in scintillators. Here, we compare and contrast the nonproportionality as registered by gamma rays and high-energy electrons. As has been noted in the past, these two types of data have different curve shapes (for plots of the light yield against electron or gamma energy). Herein, we show how the experimental gamma nonproportionality curve can be calculated from the electron response by accounting for the distribution of high energy electrons created by the gamma photon via the photoelectric interaction. Similarly, we measure and model the gamma-induced resolution as a function of energy and compare this data to predictions from our model. The utility of the model is explored using data acquired with the scintillators (Eu), GYGAG(Ce) and CsI(Na).
关键词： Gamma ray detectors,solid scintillation detectors,luminescence
更新于2025-09-23 15:21:01
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[IEEE 2019 8th International Congress on Advanced Applied Informatics (IIAI-AAI) - Toyama, Japan (2019.7.7-2019.7.11)] 2019 8th International Congress on Advanced Applied Informatics (IIAI-AAI) - Phase Type Special-Purpose Computer for Electroholography in Embedded Systems
摘要： This paper is the fifth in a series of articles on the basic physics of light yield nonproportionality in scintillators. Here, we compare and contrast the nonproportionality as registered by gamma rays and high-energy electrons. As has been noted in the past, these two types of data have different curve shapes (for plots of the light yield against electron or gamma energy). Herein, we show how the experimental gamma nonproportionality curve can be calculated from the electron response by accounting for the distribution of high energy electrons created by the gamma photon via the photoelectric interaction. Similarly, we measure and model the gamma-induced resolution as a function of energy and compare this data to predictions from our model. The utility of the model is explored using data acquired with the scintillators (Eu), GYGAG(Ce) and CsI(Na).
关键词： Gamma ray detectors,solid scintillation detectors,luminescence
更新于2025-09-23 15:21:01
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High-selectivity bandpass filter using six pairs of quarter-wavelength coupled lines
摘要： We present a 16-channel readout integrated circuit (ROIC) with nanosecond-resolution time to digital converter (TDC) for pixelated Cadmium Telluride (CdTe) gamma-ray detectors. The pixel array ROIC is the proof of concept of the pixel array readout ASIC for positron-emission tomography (PET) scanner, positron-emission mammography (PEM) scanner, and Compton gamma camera. The electronics of each individual pixel integrates an analog front-end with switchable gain, an analog to digital converter (ADC), configuration registers, and a 4-state digital controller. For every detected photon, the pixel electronics provides the energy deposited in the detector with 10-bit resolution, and a fast trigger signal for time stamp. The ASIC contains the 16-pixel matrix electronics, a digital controller, five global voltage references, a TDC, a temperature sensor, and a band-gap based current reference. The ASIC has been fabricated with TSMC m mixed-signal CMOS technology and occupies an area of mm. The TDC shows a resolution mm of 95.5 ps, a precision of 600 ps at full width half maximum W. In acquisition (FWHM), and a power consumption of mode, the total power consumption of every pixel is W. An equivalent noise charge (ENC) of at maximum gain and negative polarity conditions has been measured at room temperature.
关键词： positron emission tomography,low-power electronics,semiconductor radiation detectors,application specific integrated circuits,gamma-ray detectors,Analog-digital conversion,energy resolution
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Doped Layer Characterization Using Accurate Optical Modelling of Mid-Infrared Spectrometry
摘要： We present a 16-channel readout integrated circuit (ROIC) with nanosecond-resolution time to digital converter (TDC) for pixelated Cadmium Telluride (CdTe) gamma-ray detectors. The pixel array ROIC is the proof of concept of the pixel array readout ASIC for positron-emission tomography (PET) scanner, positron-emission mammography (PEM) scanner, and Compton gamma camera. The electronics of each individual pixel integrates an analog front-end with switchable gain, an analog to digital converter (ADC), con?guration registers, and a 4-state digital controller. For every detected photon, the pixel electronics provides the energy deposited in the detector with 10-bit resolution, and a fast trigger signal for time stamp. The ASIC contains the 16-pixel matrix electronics, a digital controller, ?ve global voltage references, a TDC, a temperature sensor, and a band-gap based current reference. The ASIC has been fabricated with TSMC m mixed-signal CMOS technology and occupies an area of mm. The TDC shows a resolution mm of 95.5 ps, a precision of 600 ps at full width half maximum W. In acquisition (FWHM), and a power consumption of mode, the total power consumption of every pixel is W. An equivalent noise charge (ENC) of at maximum gain and negative polarity conditions has been measured at room temperature.
关键词： positron emission tomography,low-power electronics,application speci?c integrated circuits,semiconductor radiation detectors,gamma-ray detectors,Analog-digital conversion,energy resolution
更新于2025-09-23 15:21:01
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Surface Waveguide Leaky-wave Antenna for Single-Side Beam Scanning
摘要： We present a 16-channel readout integrated circuit (ROIC) with nanosecond-resolution time to digital converter (TDC) for pixelated Cadmium Telluride (CdTe) gamma-ray detectors. The pixel array ROIC is the proof of concept of the pixel array readout ASIC for positron-emission tomography (PET) scanner, positron-emission mammography (PEM) scanner, and Compton gamma camera. The electronics of each individual pixel integrates an analog front-end with switchable gain, an analog to digital converter (ADC), configuration registers, and a 4-state digital controller. For every detected photon, the pixel electronics provides the energy deposited in the detector with 10-bit resolution, and a fast trigger signal for time stamp. The ASIC contains the 16-pixel matrix electronics, a digital controller, five global voltage references, a TDC, a temperature sensor, and a band-gap based current reference. The ASIC has been fabricated with TSMC m mixed-signal CMOS technology and occupies an area of mm. The TDC shows a resolution mm of 95.5 ps, a precision of 600 ps at full width half maximum W. In acquisition (FWHM), and a power consumption of mode, the total power consumption of every pixel is W. An equivalent noise charge (ENC) of at maximum gain and negative polarity conditions has been measured at room temperature.
关键词： gamma-ray detectors,low-power electronics,Analog-digital conversion,semiconductor radiation detectors,application specific integrated circuits,positron emission tomography,energy resolution
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Sandwich in the Middle: Enhancing the Optomechanical Coupling
摘要： This paper is the fifth in a series of articles on the basic physics of light yield nonproportionality in scintillators. Here, we compare and contrast the nonproportionality as registered by gamma rays and high-energy electrons. As has been noted in the past, these two types of data have different curve shapes (for plots of the light yield against electron or gamma energy). Herein, we show how the experimental gamma nonproportionality curve can be calculated from the electron response by accounting for the distribution of high energy electrons created by the gamma photon via the photoelectric interaction. Similarly, we measure and model the gamma-induced resolution as a function of energy and compare this data to predictions from our model. The utility of the model is explored using data acquired with the scintillators (Eu), GYGAG(Ce) and CsI(Na).
关键词： Gamma ray detectors,luminescence,solid scintillation detectors
更新于2025-09-19 17:13:59
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Numerical estimation of lattice strain, bending and generation of misfit dislocations in HgCdTe heterostructures grown on GaAs substrate
摘要： This paper is the fifth in a series of articles on the basic physics of light yield nonproportionality in scintillators. Here, we compare and contrast the nonproportionality as registered by gamma rays and high-energy electrons. As has been noted in the past, these two types of data have different curve shapes (for plots of the light yield against electron or gamma energy). Herein, we show how the experimental gamma nonproportionality curve can be calculated from the electron response by accounting for the distribution of high energy electrons created by the gamma photon via the photoelectric interaction. Similarly, we measure and model the gamma-induced resolution as a function of energy and compare this data to predictions from our model. The utility of the model is explored using data acquired with the scintillators (Eu), GYGAG(Ce) and CsI(Na).
关键词： Gamma ray detectors,solid scintillation detectors,luminescence
更新于2025-09-16 10:30:52
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Comparative Investigation of Gamma Radiation Effects on Long Period Gratings and Optical Power in Different Optical Fibers
摘要： This work presents a comparative study regarding the effects of gamma radiation on standard and different radiation hardened optical fibers, by means of arc-induced long period gratings (LPGs) written in these fibers. In particular, the resonance wavelength shift (Δλres) of LPG attenuation bands and the attenuation in the fiber transmitted optical power (ΔP) have been comparatively explored during irradiation. Different responses were observed depending on the fiber model. The Ge-doped fiber exhibits significant changes of both resonance wavelength and optical transmission loss, whereas the pure silica core fiber is mostly insensitive to radiation (Δλres and ΔP keep almost close to zero). Surprisingly, the radiation resistant fiber, with doped core, exhibits significant resonance shift even if with trivial power losses. In addition, by combining these results with numerical modeling of LPGs, we were able to estimate the radiation effects on the optical fibers under investigation, in terms of average refractive index change. These results can be useful for the application of such devices in radiation environments, i.e., for the development of both radiation sensitive and radiation hardened sensors.
关键词： optical fiber sensors,Gamma-ray effects,Gamma-ray detectors,optical fiber applications,Dosimetry,long period gratings
更新于2025-09-11 14:15:04