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Du J, Du S. Performance Comparison of DOI-Encoding PET Detectors Based on 1.1-mm Pitch BGO Arrays With Different Reflectors. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2024; 8:257-262. [PMID: 39279872 PMCID: PMC11392223 DOI: 10.1109/trpms.2024.3361891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/18/2024]
Abstract
Bismuth germanate (BGO)-based positron emission tomography (PET) detectors are potential candidates for low-dose imaging PET scanners, owing to the high stopping power and low background radiation of BGO. In this paper, we compared the performance of two dual-ended readout PET detectors based on 15 × 15 BGO arrays. Both arrays had the same 1.1 mm pitch but utilized different reflectors - barium sulfate (BaSO4) and enhanced specular reflector film (ESR) - for high-resolution PET applications. The detectors were constructed with Hamamatsu 13361-2050-08 SiPM arrays. Each BGO element had dimensions of 1.02 × 1.02 × 20 mm3. The lateral surfaces of the BGO elements were unpolished (saw-cut), while the two ends were polished. Flood histograms showed that the detector based on the BGO array with BaSO4 reflector had much better crystal identification and depth-of-interaction (DOI) resolution. Specifically, the energy, DOI, and timing resolutions for the detector using the BGO array with BaSO4 reflector were 19.8 ± 1.5%, 4.13 ± 0.48 mm, and 2.80 ± 0.23 ns, respectively. In contrast, the values obtained using the BGO array with ESR reflector were 20.9 ± 2.1%, 7.69 ± 1.92 mm, and 2.93 ± 0.20 ns, respectively.
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Affiliation(s)
- Junwei Du
- Department of Biomedical Engineering, University of California at Davis, Davis, CA, 95616 USA
| | - Shixian Du
- Department of Biomedical Engineering, University of California at Davis and now is with the Department of Radiology & Biomedical Imaging, University of California at San Francisco, San Francisco, CA, 94107 USA
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Du J, Jones T. Technical opportunities and challenges in developing total-body PET scanners for mice and rats. EJNMMI Phys 2023; 10:2. [PMID: 36592266 PMCID: PMC9807733 DOI: 10.1186/s40658-022-00523-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 12/20/2022] [Indexed: 01/03/2023] Open
Abstract
Positron emission tomography (PET) is the most sensitive in vivo molecular imaging technique available. Small animal PET has been widely used in studying pharmaceutical biodistribution and disease progression over time by imaging a wide range of biological processes. However, it remains true that almost all small animal PET studies using mouse or rat as preclinical models are either limited by the spatial resolution or the sensitivity (especially for dynamic studies), or both, reducing the quantitative accuracy and quantitative precision of the results. Total-body small animal PET scanners, which have axial lengths longer than the nose-to-anus length of the mouse/rat and can provide high sensitivity across the entire body of mouse/rat, can realize new opportunities for small animal PET. This article aims to discuss the technical opportunities and challenges in developing total-body small animal PET scanners for mice and rats.
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Affiliation(s)
- Junwei Du
- grid.27860.3b0000 0004 1936 9684Department of Biomedical Engineering, University of California at Davis, Davis, CA 95616 USA
| | - Terry Jones
- grid.27860.3b0000 0004 1936 9684Department of Radiology, University of California at Davis, Davis, CA 95616 USA
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Yang Q, Wang X, Kuang Z, Zhang C, Yang Y, Du J. Evaluation of Two SiPM Arrays for Depth-Encoding PET Detectors Based on Dual-Ended Readout. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2021. [DOI: 10.1109/trpms.2020.3008710] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Lai Y, Wang Q, Zhou S, Xie Z, Qi J, Cherry SR, Jin M, Chi Y, Du J. H 2RSPET: a 0.5 mm resolution high-sensitivity small-animal PET scanner, a simulation study. Phys Med Biol 2021; 66:065016. [PMID: 33571980 DOI: 10.1088/1361-6560/abe558] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
With the goal of developing a total-body small-animal PET system with a high spatial resolution of ∼0.5 mm and a high sensitivity >10% for mouse/rat studies, we simulated four scanners using the graphical processing unit-based Monte Carlo simulation package (gPET) and compared their performance in terms of spatial resolution and sensitivity. We also investigated the effect of depth-of-interaction (DOI) resolution on the spatial resolution. All the scanners are built upon 128 DOI encoding dual-ended readout detectors with lutetium yttrium oxyorthosilicate (LYSO) arrays arranged in 8 detector rings. The solid angle coverages of the four scanners are all ∼0.85 steradians. Each LYSO element has a cross-section of 0.44 × 0.44 mm2 and the pitch size of the LYSO arrays are all 0.5 mm. The four scanners can be divided into two groups: (1) H2RS110-C10 and H2RS110-C20 with 40 × 40 LYSO arrays, a ring diameter of 110 mm and axial length of 167 mm, and (2) H2RS160-C10 and H2RS160-C20 with 60 × 60 LYSO arrays, a diameter of 160 mm and axial length of 254 mm. C10 and C20 denote the crystal thickness of 10 and 20 mm, respectively. The simulation results show that all scanners have a spatial resolution better than 0.5 mm at the center of the field-of-view (FOV). The radial resolution strongly depends on the DOI resolution and radial offset, but not the axial resolution and tangential resolution. Comparing the C10 and C20 designs, the former provides better resolution, especially at positions away from the center of the FOV, whereas the latter has 2× higher sensitivity (∼10% versus ∼20%). This simulation study provides evidence that the 110 mm systems are a good choice for total-body mouse studies at a lower cost, whereas the 160 mm systems are suited for both total-body mouse and rat studies.
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Affiliation(s)
- Youfang Lai
- Department of Physics, University of Texas at Arlington, Arlington, TX 76019, United States of America
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Zhao T, Dai L, Peng Y, Li B, Liu J, Liang K, Yang R, Han D. Feasibility of High-Resolution PET Detector Readout by 2-D Tetra-Lateral Position-Sensitive Silicon Photomultiplier. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2019. [DOI: 10.1109/trpms.2018.2878410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Du J, Bai X, Cherry SR. A depth-of-interaction encoding PET detector module with dual-ended readout using large-area silicon photomultiplier arrays. Phys Med Biol 2018; 63:245019. [PMID: 30523925 DOI: 10.1088/1361-6560/aaee32] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The performance of a depth-of-interaction (DOI) encoding PET detector module with dual-ended readout of LYSO scintillator arrays using large-area SiPM arrays was evaluated. Each SiPM array, with a surface area of 50.2 × 50.2 mm2, consists of 12 × 12 C-series SiPMs from SensL (SensL, Inc). The LYSO array, with a total size of 46 × 46 mm2 and a pitch size of 1.0 mm, consists of a 46 × 46 array of 0.945 × 0.945 × 20 mm3 polished LYSO crystals, separated by Toray reflector. Custom front-end electronics were designed to reduce the 288 SiPM signals of one detector module to nine signals, eight for position information and 1 for timing information. Schottky diodes were used to block noise from SiPMs that did not detect a significant number of scintillation photons following a gamma interaction. Measurements of noise, signal, signal-to-noise ratio, energy resolution and flood histogram quality were obtained at different bias voltages (26.0 to 31.0 V in 0.5 V intervals) and at two temperatures (5 °C and 20 °C). Clear acrylic plates, 2.0 mm thick, were used as light guides to spread the scintillation photons. Timing resolution, depth of interaction resolution, and the effect of event rate on detector performance were measured at the bias voltage determined to be optimal for the flood histograms. Performance obtained with and without the noise-blocking Shottky diodes was also compared. The results showed that all crystals in the LYSO array can be clearly resolved, and performance improved when using diodes to block noise, and at the lower temperature. The average energy resolution, flood histogram quality, timing resolution and DOI resolution were 23.8% ± 2.0%, 1.54 ± 0.17, 1.78 ± 0.09 ns and 2.81 ± 0.13 mm respectively, obtained at a bias voltage of 30.0 V and a temperature of 5 °C using the diode readout method. The event rate experiments showed that the flood histogram and energy resolution of the detector were not significantly degraded for an event rate of up to 150 000 counts s-1.
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Affiliation(s)
- Junwei Du
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, CA 95616, United States of America
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Du J, Bai X, Gola A, Acerbi F, Ferri A, Piemonte C, Yang Y, Cherry SR. Performance of a high-resolution depth-encoding PET detector module using linearly-graded SiPM arrays. Phys Med Biol 2018; 63:035035. [PMID: 29324437 PMCID: PMC5823499 DOI: 10.1088/1361-6560/aaa707] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The goal of this study was to exploit the excellent spatial resolution characteristics of a position-sensitive silicon photomultiplier (SiPM) and develop a high-resolution depth-of-interaction (DOI) encoding positron emission tomography (PET) detector module. The detector consists of a 30 × 30 array of 0.445 × 0.445 × 20 mm3 polished LYSO crystals coupled to two 15.5 × 15.5 mm2 linearly-graded SiPM (LG-SiPM) arrays at both ends. The flood histograms show that all the crystals in the LYSO array can be resolved. The energy resolution, the coincidence timing resolution and the DOI resolution were 21.8 ± 5.8%, 1.23 ± 0.10 ns and 3.8 ± 1.2 mm, respectively, at a temperature of -10 °C and a bias voltage of 35.0 V. The performance did not degrade significantly for event rates of up to 130 000 counts s-1. This detector represents an attractive option for small-bore PET scanner designs that simultaneously emphasize high spatial resolution and high detection efficiency, important, for example, in preclinical imaging of the rodent brain with neuroreceptor ligands.
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Affiliation(s)
- Junwei Du
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, CA 95616, United States of America
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Du J, Schmall JP, Di K, Yang Y, Dokhale PA, Shah KS, Cherry SR. Performance Comparison of Different Readouts for Position-Sensitive Solid-State Photomultiplier Arrays. Biomed Phys Eng Express 2017; 3. [PMID: 29915669 DOI: 10.1088/2057-1976/aa7c6a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A thorough comparison of five different readouts for reading out a 2 × 2 array of 5 mm × 5 mm position-sensitive solid-state photomultipliers (PS-SSPM) was undertaken. The five readouts include reading out the 20 signals (16 position and 4 timing) individually, two signal multiplexing readouts, and two position decoding readouts. Flood histogram quality, signal-to-noise ratio (SNR) and energy resolution were compared at different bias voltage (27.0 V to 32.0 V, at 0.5 V intervals) and at a fixed temperature of 0 °C by coupling a 6 × 6 array of 1.3 mm × 1.3 mm × 20 mm polished LSO crystals to the center of the PS-SSPM array. The timing resolution was measured at a bias voltage of 31.0 V (optimal bias voltage in terms of flood histogram quality). The best flood histogram quality value and signal-to-noise were 7.3 ± 1.6 and 33.5 ± 3.1, respectively, and were obtained by shaping and digitizing the 16 position signals individually. The capacitive charge-division readout is the simplest readout among the five evaluated but still resulted in good performance with a flood histogram quality value of 3.3 ± 0.4 and a SNR of 18.3 ± 1.3. The average energy resolution and the average timing resolution were 15.2 ± 1.2 % and 8.4 ± 1.6 ns for individual signal readout and 15.9 ± 1.2 % and 8.8 ± 1.3 ns by using the capacitive charge-division readout method. These studies show that for an ultra-high spatial resolution applications using the 2 × 2 PS-SSPM array, reading out the 20 signals individually is necessary; whilst the capacitive charge-division readout is a cost-effective readout for less demanding applications.
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Affiliation(s)
- Junwei Du
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Jeffrey P Schmall
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Kun Di
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Yongfeng Yang
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | | | - Kanai S Shah
- Radiation Monitoring Devices Inc., Watertown, MA 02172, USA
| | - Simon R Cherry
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
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Park H, Ko GB, Lee JS. Hybrid charge division multiplexing method for silicon photomultiplier based PET detectors. Phys Med Biol 2017; 62:4390-4405. [DOI: 10.1088/1361-6560/aa6aea] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Du J, Yang Y, Bai X, Judenhofer MS, Berg E, Di K, Buckley S, Jackson C, Cherry SR. Characterization of Large-Area SiPM Array for PET Applications. IEEE TRANSACTIONS ON NUCLEAR SCIENCE 2016; 63:8-16. [PMID: 27182077 PMCID: PMC4863987 DOI: 10.1109/tns.2015.2499726] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The performance of an 8 × 8 array of 6.0 × 6.0 mm2 (active area) SiPMs was evaluated for PET applications using crystal arrays with different pitch sizes (3.4 mm, 1.5 mm, 1.35 mm and 1.2 mm) and custom designed five-channel front-end readout electronics (four channels for position information and one channel for timing information). The total area of this SiPM array is 57.4 × 57.4 mm2, and the pitch size is 7.2 mm. It was fabricated using enhanced blue sensitivity SiPMs (MicroFB-60035-SMT) with peak spectral sensitivity at 420 nm. The performance of the SiPM array was characterized by measuring flood histogram decoding quality, energy resolution, timing resolution and saturation at several bias voltages (from 25.0 V to 30.0 V in 0.5 V intervals) and two different temperatures (5 °C and 20 °C). Results show that the best flood histogram was obtained at a bias voltage of 28.0 V and 5 °C and an array of polished LSO crystals with a pitch as small as 1.2 mm can be resolved. No saturation was observed up to a bias voltage of 29.5 V during the experiments, due to adequate light sharing between SiPMs. Energy resolution and timing resolution at 5 °C ranged from 12.7 ± 0.8% to 14.6 ± 1.4 % and 1.58 ± 0.13 ns to 2.50 ± 0.44 ns, for crystal array pitch sizes of 3.4 mm and 1.2 mm respectively. Superior flood histogram quality, energy resolution and timing resolution were obtained with larger crystal array pitch sizes and at lower temperature. Based on our findings, we conclude that this large-area SiPM array can serve as a suitable photodetector for high-resolution small-animal PET or dedicated human brain PET scanners.
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Affiliation(s)
- Junwei Du
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Yongfeng Yang
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Xiaowei Bai
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Martin S Judenhofer
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Eric Berg
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Kun Di
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Steve Buckley
- SensL Technologies Ltd., 6800 Airport Business Park, Cork, Ireland
| | - Carl Jackson
- SensL Technologies Ltd., 6800 Airport Business Park, Cork, Ireland
| | - Simon R Cherry
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
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Du J, Yang Y, Berg E, Bai X, Gola A, Ferri A, Zorzi N, Piemonte C, Cherry SR. Evaluation of linearly-graded SiPMs for high resolution small-animal PET. Biomed Phys Eng Express 2015. [DOI: 10.1088/2057-1976/1/4/045008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Du J, Schmall JP, Di K, Yang Y, Judenhofer M, Bec J, Buckley S, Jackson C, Cherry SR. Design and optimization of a high-resolution PET detector module for small-animal PET based on a 12 × 12 silicon photomultiplier array. Biomed Phys Eng Express 2015. [DOI: 10.1088/2057-1976/1/4/045003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Du J, Schmall JP, Yang Y, Di K, Roncali E, Mitchell GS, Buckley S, Jackson C, Cherry SR. Evaluation of Matrix9 silicon photomultiplier array for small-animal PET. Med Phys 2015; 42:585. [PMID: 25652479 DOI: 10.1118/1.4905088] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The MatrixSL-9-30035-OEM (Matrix9) from SensL is a large-area silicon photomultiplier (SiPM) photodetector module consisting of a 3 × 3 array of 4 × 4 element SiPM arrays (total of 144 SiPM pixels) and incorporates SensL's front-end electronics board and coincidence board. Each SiPM pixel measures 3.16 × 3.16 mm(2) and the total size of the detector head is 47.8 × 46.3 mm(2). Using 8 × 8 polished LSO/LYSO arrays (pitch 1.5 mm) the performance of this detector system (SiPM array and readout electronics) was evaluated with a view for its eventual use in small-animal positron emission tomography (PET). METHODS Measurements of noise, signal, signal-to-noise ratio, energy resolution, flood histogram quality, timing resolution, and array trigger error were obtained at different bias voltages (28.0-32.5 V in 0.5 V intervals) and at different temperatures (5 °C-25 °C in 5 °C degree steps) to find the optimal operating conditions. RESULTS The best measured signal-to-noise ratio and flood histogram quality for 511 keV gamma photons were obtained at a bias voltage of 30.0 V and a temperature of 5 °C. The energy resolution and timing resolution under these conditions were 14.2% ± 0.1% and 4.2 ± 0.1 ns, respectively. The flood histograms show that all the crystals in the 1.5 mm pitch LSO array can be clearly identified and that smaller crystal pitches can also be resolved. Flood histogram quality was also calculated using different center of gravity based positioning algorithms. Improved and more robust results were achieved using the local 9 pixels for positioning along with an energy offset calibration. To evaluate the front-end detector readout, and multiplexing efficiency, an array trigger error metric is introduced and measured at different lower energy thresholds. Using a lower energy threshold greater than 150 keV effectively eliminates any mispositioning between SiPM arrays. CONCLUSIONS In summary, the Matrix9 detector system can resolve high-resolution scintillator arrays common in small-animal PET with adequate energy resolution and timing resolution over a large detector area. The modular design of the Matrix9 detector allows it to be used as a building block for simple, low channel-count, yet high performance, small animal PET or PET/MRI systems.
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Affiliation(s)
- Junwei Du
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Jeffrey P Schmall
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Yongfeng Yang
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Kun Di
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Emilie Roncali
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Gregory S Mitchell
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Steve Buckley
- SensL Technologies Ltd., 6800 Airport Business Park, Cork, Ireland
| | - Carl Jackson
- SensL Technologies Ltd., 6800 Airport Business Park, Cork, Ireland
| | - Simon R Cherry
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California, 95616
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Schmall JP, Du J, Judenhofer MS, Dokhale P, Christian J, McClish M, Shah KS, Cherry SR. A Study of Position-Sensitive Solid-State Photomultiplier Signal Properties. IEEE TRANSACTIONS ON NUCLEAR SCIENCE 2014; 61:1074-1083. [PMID: 25473125 PMCID: PMC4249698 DOI: 10.1109/tns.2014.2302635] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We present an analysis of the signal properties of a position-sensitive solid-state photomultiplier (PS-SSPM) that has an integrated resistive network for position sensing. Attractive features of PS-SSPMs are their large area and ability to resolve small scintillator crystals. However, the large area leads to a high detector capacitance, and in order to achieve high spatial resolution a large network resistor value is required. These inevitably create a low-pass filter that drastically slows what would be a fast micro-cell discharge pulse. Significant changes in the signal shape of the PS-SSPM cathode output as a function of position are observed, which result in a position-dependent time delay when using traditional time pick-off methods such as leading edge discrimination and constant fraction discrimination. The timing resolution and time delay, as a function of position, were characterized for two different PS-SSPM designs, a continuous 10 mm × 10 mm PS-SSPM and a tiled 2 × 2 array of 5 mm × 5 mm PS-SSPMs. After time delay correction, the block timing resolution, measured with a 6 × 6 array of 1.3 × 1.3 × 20 mm3 LSO crystals, was 8.6 ns and 8.5 ns, with the 10 mm PS-SSPM and 5 mm PS-SSPM respectively. The effect of crystal size on timing resolution was also studied, and contrary to expectation, a small improvement was measured when reducing the crystal size from 1.3 mm to 0.5 mm. Digital timing methods were studied and showed great promise for allowing accurate timing by implementation of a leading edge time pick-off. Position-dependent changes in signal shape on the anode side also are present, which complicates peak height data acquisition methods used for positioning. We studied the effect of trigger position on signal amplitude, flood histogram quality, and depth-of-interaction resolution in a dual-ended readout detector configuration. We conclude that detector timing and positioning can be significantly improved by implementation of digital timing methods and by accounting for changes in the shape of the signals from PS-SSPMs.
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Affiliation(s)
- Jeffrey P Schmall
- Department of Biomedical Engineering, University of California - Davis, CA, 95616 USA
| | - Junwei Du
- Department of Biomedical Engineering, University of California - Davis, CA, 95616 USA
| | - Martin S Judenhofer
- Department of Biomedical Engineering, University of California - Davis, CA, 95616 USA
| | | | | | - Mickel McClish
- Radiation Monitoring Devices Inc., Watertown, MA, 02472 USA
| | - Kanai S Shah
- Radiation Monitoring Devices Inc., Watertown, MA, 02472 USA
| | - Simon R Cherry
- Department of Biomedical Engineering, University of California - Davis, CA, 95616 USA
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Du J, Schmall JP, Yang Y, Di K, Dokhale PA, Shah KS, Cherry SR. A Simple Capacitive Charge-Division Readout for Position-Sensitive Solid-State Photomultiplier Arrays. IEEE TRANSACTIONS ON NUCLEAR SCIENCE 2013; 60:3188-3197. [PMID: 25558081 PMCID: PMC4281963 DOI: 10.1109/tns.2013.2275012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
A capacitive charge-division readout method for reading out a 2 × 2 array of 5 mm × 5 mm position-sensitive solid-state photomultipliers (PS-SSPM) was designed and evaluated. Using this analog multiplexing method, the 20 signals (16 position, 4 timing) from the PS-SSPM array are reduced to 5 signals (4 position, 1 timing), allowing the PS-SSPM array to be treated as an individual large-area PS-SSPM module. A global positioning approach can now be used, instead of individual positioning for each PS-SSPM in the array, ensuring that the entire light signal is utilized. The signal-to-noise ratio (SNR) and flood histogram quality at different bias voltages (27.5 V to 32.0 V at 0.5 V intervals) and a fixed temperature of 0 °C were evaluated by coupling a 6 × 6 array of 1.3 mm × 1.3 mm × 20 mm polished LSO crystals to the center of the PS-SSPM array. The timing resolution was measured at a fixed bias voltage of 31.0 V and a fixed temperature of 0 °C. All the measurements were evaluated and compared using capacitors with different values and tolerances. Capacitor values ranged from 0.051 nf to 10 nf, and the capacitance tolerance ranged from 1% to 20%. The results show that better performance was achieved using capacitors with smaller values and better capacitance tolerance. Using 0.2 nf capacitors, the SNR, energy resolution and timing resolution were 24.3, 18.2% and 8.8 ns at a bias voltage 31.0 V, respectively. The flood histogram quality was also evaluated by using a 10 × 10 array of 1 mm × 1 mm × 10 mm polished LSO crystals and a 10 × 10 array of 0.7 mm × 0.7 mm × 20 mm unpolished LSO crystals to determine the smallest crystal size resolvable. These studies showed that the high spatial resolution of the PS-SSPM was preserved allowing for 0.7 mm crystals to be identified. These results show that the capacitive charge-division analog signal processing method can significantly reduce the number of electronic channels, from 20 to 5, while retaining the excellent performance of the detector.
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Affiliation(s)
- Junwei Du
- Department of Biomedical Engineering, University of California, Davis, CA 95616, USA
| | - Jeffrey P. Schmall
- Department of Biomedical Engineering, University of California, Davis, CA 95616, USA
| | - Yongfeng Yang
- Department of Biomedical Engineering, University of California, Davis, CA 95616, USA
| | - Kun Di
- Department of Biomedical Engineering, University of California, Davis, CA 95616, USA
| | | | - Kanai S. Shah
- Radiation Monitoring Devices Inc., Watertown, MA 02172, USA
| | - Simon R. Cherry
- Department of Biomedical Engineering, University of California, Davis, CA 95616, USA
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Bieniosek MF, Olcott PD, Levin CS. Compact pulse width modulation circuitry for silicon photomultiplier readout. Phys Med Biol 2013; 58:5049-59. [PMID: 23831601 DOI: 10.1088/0031-9155/58/15/5049] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The adoption of solid-state photodetectors for positron emission tomography (PET) system design and the interest in 3D interaction information from PET detectors has lead to an increasing number of readout channels in PET systems. To handle these additional readout channels, PET readout electronics should be simplified to reduce the power consumption, cost, and size of the electronics for a single channel. Pulse-width modulation (PWM), where detector pulses are converted to digital pulses with width proportional to the detected photon energy, promises to simplify PET readout by converting the signals to digital form at the beginning of the processing chain, and allowing a single time-to-digital converter to perform the data acquisition for many channels rather than routing many analogue channels and digitizing in the back end. Integrator based PWM systems, also known as charge-to-time converters (QTCs), are especially compact, reducing the front-end electronics to an op-amp integrator with a resistor discharge, and a comparator. QTCs, however, have a long dead-time during which dark count noise is integrated, reducing the output signal-to-noise ratio. This work presents a QTC based PWM circuit with a gated integrator that shows performance improvements over existing QTC based PWM. By opening and closing an analogue switch on the input of the integrator, the circuit can be controlled to integrate only the portions of the signal with a high signal-to-noise ratio. It also allows for multiplexing different detectors into the same PWM circuit while avoiding uncorrelated noise propagation between photodetector channels. Four gated integrator PWM circuits were built to readout the spatial channels of two position sensitive solid-state photomultiplier (PS-SSPM). Results show a 4 × 4 array 0.9 mm × 0.9 mm × 15 mm of LYSO crystals being identified on the 5 mm × 5 mm PS-SSPM at room temperature with no degradation for twofold multiplexing. In principle, much larger multiplexing ratios are possible, limited only by count rate issues.
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Affiliation(s)
- M F Bieniosek
- Department of Radiology, Stanford University, Stanford, CA 94305, USA.
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