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Correia PMM, Cruzeiro B, Dias J, Encarnação PMCC, Ribeiro FM, Rodrigues CA, Silva ALM. Precise positioning of gamma ray interactions in multiplexed pixelated scintillators using artificial neural networks. Biomed Phys Eng Express 2024; 10:045038. [PMID: 38779912 DOI: 10.1088/2057-1976/ad4f73] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Accepted: 05/22/2024] [Indexed: 05/25/2024]
Abstract
Introduction. The positioning ofγray interactions in positron emission tomography (PET) detectors is commonly made through the evaluation of the Anger logic flood histograms. machine learning techniques, leveraging features extracted from signal waveform, have demonstrated successful applications in addressing various challenges in PET instrumentation.Aim. This paper evaluates the use of artificial neural networks (NN) forγray interaction positioning in pixelated scintillators coupled to a multiplexed array of silicon photomultipliers (SiPM).Methods. An array of 16 Cerium doped Lutetium-based (LYSO) crystal pixels (cross-section 2 × 2 mm2) coupled to 16 SiPM (S13360-1350) were used for the experimental setup. Data from each of the 16 LYSO pixels was recorded, a total of 160000 events. The detectors were irradiated by 511 keV annihilationγrays from a Sodium-22 (22Na) source. Another LYSO crystal was used for electronic collimation. Features extracted from the signal waveform were used to train the model. Two models were tested: i) single multiple-class neural network (mcNN), with 16 possible outputs followed by a softmax and ii) 16 binary classification neural networks (bNN), each one specialized in identifying events occurred in each position.Results. Both NN models showed a mean positioning accuracy above 85% on the evaluation dataset, although the mcNN is faster to train.DiscussionThe method's accuracy is affected by the introduction of misclassified events that interacted in the neighbour's crystals and were misclassified during the dataset acquisition. Electronic collimation reduces this effect, however results could be improved using a more complex acquisition setup, such as a light-sharing configuration.ConclusionsThe methods comparison showed that mcNN and bNN can surpass the Anger logic, showing the feasibility of using these models in positioning procedures of future multiplexed detector systems in a linear configuration.
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Affiliation(s)
- P M M Correia
- Institute for Nanostructures, Nanomodelling and Nanofabrication (i3N), University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal
| | - B Cruzeiro
- Institute for Nanostructures, Nanomodelling and Nanofabrication (i3N), University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal
| | - J Dias
- Faculdade de Economia, CeBER, Universidade de Coimbra, Av. Dias da Silva, 165, 3004-512 Coimbra, Portugal
- INESC-Coimbra, Universidade de Coimbra, Rua Sílvio Lima, Pólo II, 3030-290 Coimbra, Portugal
| | - P M C C Encarnação
- Institute for Nanostructures, Nanomodelling and Nanofabrication (i3N), University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal
| | - F M Ribeiro
- Institute for Nanostructures, Nanomodelling and Nanofabrication (i3N), University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal
| | - C A Rodrigues
- Institute for Nanostructures, Nanomodelling and Nanofabrication (i3N), University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal
| | - A L M Silva
- Institute for Nanostructures, Nanomodelling and Nanofabrication (i3N), University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal
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Gonzalez-Montoro A, Levin CS. PET System Technology: Theoretical Aspects and Experimental Methodology. Methods Mol Biol 2024; 2729:343-369. [PMID: 38006506 DOI: 10.1007/978-1-0716-3499-8_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2023]
Abstract
Positron emission tomography (PET) imaging provides unique information of the cellular and molecular pathways of disease occurring within the human body, using measurements made from outside the body, which has shown utility in a variety of studies from basic research to clinical applications. This chapter describes some of the most relevant PET system parameters that impact its imaging performance such as 3D spatial, energy, and coincidence timing resolutions and the methodology typically used to evaluate those parameters. In addition, the physical principles underlying PET imaging, PET photon detector technology, and coincidence detection are also described. As a closing remark, the future perspectives of PET imaging and its simultaneous use with anatomical imaging techniques (e.g., computed tomography [CT] and magnetic resonance imaging [MRI]) are outlined.
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Affiliation(s)
| | - Craig S Levin
- Department of Radiology, Stanford University, Stanford, CA, USA.
- Departments of Radiology, Bioengineering, Physics, and Electrical Engineering, Stanford University, Stanford, CA, USA.
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Li Y, Zeng X, Goldan AH. Decision Tree-Based Demultiplexing for Prism-PET. IEEE TRANSACTIONS ON NUCLEAR SCIENCE 2023; 70:1425-1430. [PMID: 38680514 PMCID: PMC11044823 DOI: 10.1109/tns.2023.3282831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/01/2024]
Abstract
Signal multiplexing is necessary to reduce a large number of readout channels in positron emission tomography (PET) scanners to minimize cost and achieve lower power consumption. However, the conventional weighted average energy method cannot localize the multiplexed events and more sophisticated approaches are necessary for accurate demultiplexing. The purpose of this paper is to propose a non-parametric decision tree model for demultiplexing signals in prismatoid PET (Prism-PET) detector module that consisted of 16 × 16 lutetium yttrium oxyorthosilicate (LYSO) scintillation crystal array coupled to 8 × 8 silicon photomultiplier (SiPM) pixels with 64:16 multiplexed readout. A total of 64 regression trees were trained individually to demultiplex the encoded readouts for each SiPM pixel. The Center of Gravity (CoG) and Truncated Center of Gravity (TCoG) methods were utilized for crystal identification based on the demultiplexed pixels. The flood histogram, energy resolution, and depth-of-interaction (DOI) resolution were measured for comparison using with and without multiplexed readouts. In conclusion, our proposed decision tree model achieved accurate results for signal demultiplexing, and thus maintained the Prism-PET detector module's high spatial and DOI resolution performance while using our unique light-sharing-based multiplexed readout.
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Affiliation(s)
- Yixin Li
- Department of Electrical and Computer Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY 11794, US
- Department of Radiology, Weill Cornell Medicine, Cornell University, NY 10021, US
| | - Xinjie Zeng
- Department of Electrical and Computer Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY 11794, US
- Department of Radiology, Weill Cornell Medicine, Cornell University, NY 10021, US
| | - Amir H Goldan
- Department of Radiology, Weill Cornell Medicine, Cornell University, NY 10021, US
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Liu Z, Mungai S, Niu M, Kuang Z, Ren N, Wang X, Sang Z, Yang Y. Edge effect reduction of high-resolution PET detectors using LYSO and GAGG phoswich crystals. Phys Med Biol 2023; 68. [PMID: 36808920 DOI: 10.1088/1361-6560/acbde1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 02/21/2023] [Indexed: 02/23/2023]
Abstract
Objective. Small-animal positron emission tomography (PET) is a powerful preclinical imaging tool in animal model studies. The spatial resolution and sensitivity of current PET scanners developed for small-animal imaging need to be improved to increase the quantitative accuracy of preclinical animal studies. This study aimed to improve the identification capability of edge scintillator crystals of a PET detector which will enable to apply a crystal array with the same cross-section area as the active area of a photodetector for improving the detection area and thus reducing or eliminating the inter-detector gaps.Approach. PET detectors using crystal arrays with mixed lutetium yttrium orthosilicate (LYSO) and gadolinium aluminum gallium garnet (GAGG) crystals were developed and evaluated. The crystal arrays consisted of 31 × 31 array of 0.49 × 0.49 × 20 mm3crystals; they were read out by two silicon photomultiplier arrays with pixel sizes of 2 × 2 mm2that were placed at both ends of the crystal arrays. The second or first outermost layer of the LYSO crystals was replaced by GAGG crystals in the two crystal arrays. The two crystal types were identified using a pulse-shape discrimination technique to provide better edge crystal identification.Main results. Using the pulse shape discrimination technique, almost all (except for a few edge) crystals were resolved in the two detectors; high sensitivity was achieved by using the scintillator array and the photodetector with the same areas and achieved high resolution by using crystals with sizes equal to 0.49 × 0.49 × 20 mm3. Energy resolutions of 19.3 ± 1.8% and 18.9 ± 1.5%, depth-of-interaction resolutions of 2.02 ± 0.17 mm and 2.04 ± 0.18 mm, and timing resolutions of 1.6 ± 0.2 ns and 1.5 ± 0.2 ns were achieved by the two detectors, respectively.Significance. In summary, novel three-dimensional high-resolution PET detectors consisting of a mixture of LYSO and GAGG crystals were developed. The detectors significantly improve the detection area with the same photodetectors and thus improve the detection efficiency.
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Affiliation(s)
- Zheng Liu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
| | - Samuel Mungai
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
| | - Ming Niu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
| | - Zhonghua Kuang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
| | - Ning Ren
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
| | - Xiaohui Wang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
| | - Ziru Sang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
| | - Yongfeng Yang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
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Cong L, Kuang Z, Sang Z, Wang X, Niu M, Yang Y. Comparison of arithmetic mean and energy-weighted mean flood histogram generation methods for dual-ended readout PET detectors. Med Phys 2022; 49:4455-4465. [PMID: 35567406 DOI: 10.1002/mp.15710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Revised: 04/26/2022] [Accepted: 05/03/2022] [Indexed: 11/05/2022] Open
Abstract
PURPOSE Dual-ended readout pixelated scintillator array detectors can provide a suitable crystal resolvability and satisfactory depth of interaction (DOI), energy, and timing resolutions. Usually, the flood histogram measured by one-sided readout is depth dependent, and the flood histogram quality degrades as the distance between the interaction site and photodetector increases. Information measured by two photodetectors must be combined to obtain an improved flood histogram yielding a better PET scanner spatial resolution. METHODS Two flood histogram generation algorithms for dual-ended readout of pixelated scintillator array detectors were compared by theoretical calculations and experimental measurements. The first algorithm is the arithmetic mean (AM) algorithm, which assigns the same weight to the flood histograms measured by photodetectors 1 and 2. The second algorithm is the energy-weighted mean (EWM) algorithm, which assigns each flood histogram a certain weight proportional to the energy measured by the photodetector. Theoretical equations were derived to determine the quality of the flood histograms obtained with these two algorithms. Experimental measurements were performed with an 18 × 18 lutetium-yttrium oxyorthosilicate (LYSO) array with a crystal size of 0.62 × 0.62 × 20 mm3 read out by two multi-anode photomultiplier tubes at both ends. Flood histograms of the whole array and five specific depths were compared between the above two algorithms. RESULTS The theoretical results indicated that the flood histograms obtained with the EWM method matched those obtained with the AM method at the middle detector depth and were better at other detector depths when the distance (S) between the locations of the same crystal in the flood histograms measured by photodetectors 1 and 2 reached 0. The advantage of the EWM method decreased with increasing S value since the crystal position in the flood histogram obtained with the EWM method varies with the depth when S does not equal 0. The advantage of the EWM method decreased with increasing S value. The experimental results generally agreed with the theoretical predictions. Compared to the AM method, the EWM method provided a similar flood histogram at a depth of 10 mm but generated a better flood histogram at depths of 2 and 18 mm. Although an inverse correlation between Q (a quality factor representing the advantage of the EWM method) and S was observed, the variation in Q given the same S value was high. The average Q value at the same S still agreed with the theoretical predictions. CONCLUSIONS Theoretical equations were derived, and experimental measurements were performed to compare two flood histogram generation algorithms for dual-ended readout PET detectors. The results indicated that the EWM method based on inverse variance weighting theory could provide better flood histograms than those provided by the AM method. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Longhan Cong
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Zhonghua Kuang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Ziru Sang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Xiaohui Wang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Ming Niu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Yongfeng Yang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
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Liu Z, Niu M, Kuang Z, Ren N, Wu S, Cong L, Wang X, Sang Z, Williams C, Yang Y. High resolution detectors for whole-body PET scanners by using dual-ended readout. EJNMMI Phys 2022; 9:29. [PMID: 35445890 PMCID: PMC9023628 DOI: 10.1186/s40658-022-00460-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 04/08/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Most current whole-body positron emission tomography (PET) scanners use detectors with high timing resolution to measure the time-of-flight of two 511 keV photons, improving the signal-to-noise ratio of PET images. However, almost all current whole-body PET scanners use detectors without depth-encoding capability; therefore, their spatial resolution can be affected by the parallax effect. METHODS In this work, four depth-encoding detectors consisting of LYSO arrays with crystals of 2.98 × 2.98 × 20 mm3, 2.98 × 2.98 × 30 mm3, 1.95 × 1.95 × 20 mm3, and 1.95 × 1.95 × 30 mm3, respectively, were read at both ends, with 6 × 6 mm2 silicon photomultiplier (SiPM) pixels in a 4 × 4 array being used. The timing signals of the detectors were processed individually using an ultrafast NINO application-specific integrated circuit (ASIC) to obtain good timing resolution. The 16 energy signals of the SiPM array were read using a row and column summing circuit to obtain four position-encoding energy signals. RESULTS The four PET detectors provided good flood histograms in which all crystals could be clearly resolved, the crystal energy resolutions measured being 10.2, 12.1, 11.4 and 11.7% full width at half maximum (FWHM), at an average crystal depth of interaction (DOI) resolution of 3.5, 3.9, 2.7, and 3.0 mm, respectively. The depth dependence of the timing of each SiPM was measured and corrected, the timing of the two SiPMs being used as the timing of the dual-ended readout detector. The four detectors provided coincidence time resolutions of 180, 214, 239, and 263 ps, respectively. CONCLUSIONS The timing resolution of the dual-ended readout PET detector was approximately 20% better than that of the single-ended readout detector using the same LYSO array, SiPM array, and readout electronics. The detectors developed in this work used long crystals with small cross-sections and provided good flood histograms, DOI, energy, and timing resolutions, suggesting that they could be used to develop whole-body PET scanners with high sensitivity, uniform high spatial resolution, and high timing resolution.
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Affiliation(s)
- Zheng Liu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ming Niu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Zhonghua Kuang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ning Ren
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - San Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Longhan Cong
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Xiaohui Wang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ziru Sang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Crispin Williams
- European Centre for Nuclear Research (CERN), Geneva, Switzerland
| | - Yongfeng Yang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
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Niu M, Liu Z, Kuang Z, Wang X, Ren N, Sang Z, Wu S, Cong L, Sun T, Hu Z, Yang Y. Ultra-high resolution depth-encoding small animal PET detectors: Using GAGG and LYSO crystal arrays. Med Phys 2022; 49:3006-3020. [PMID: 35301730 DOI: 10.1002/mp.15606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 03/03/2022] [Accepted: 03/03/2022] [Indexed: 11/12/2022] Open
Abstract
PURPOSE Small animal PET scanners are widely used in current biomedical research. The study aimed to develop high efficiency and ultra-high resolution detectors that could be used to develop a small animal PET scanner with high sensitivity and spatial resolution approaching to its physical limit. METHODS 4 crystal arrays were fabricated and measured in this study. Crystal arrays 1 and 2 consisted of 38 × 38 GAGG and LYSO crystals of 0.4 × 0.4 × 20 mm3 size. Crystal array 3 consisted of 16 × 16 GAGG crystals of 0.3 × 0.3 × 20 mm3 size, and crystal array 4 consisted of 24 × 24 LYSO crystals 0.3 × 0.3 × 20 mm3 in size. The crystal arrays were dual-ended readouts using 8 × 8 SiPM arrays of 2 × 2 mm2 pixel area. The SiPM array was read-out using a signal multiplexing circuit to convert the 64 output signals into 4 position-encoding signals. The performances of the 4 detectors in terms of flood histogram, energy resolution, depth of interaction resolution and timing resolution were measured. RESULTS The GAGG detectors provided better flood histograms, ∼30% higher photopeak amplitude, ∼20% higher energy resolution, ∼12% worse DOI resolution and ∼15% worse timing resolution compared with LYSO detectors of the same crystal size. These 4 detectors provided DOI resolutions of <2 mm, energy resolutions of <22% and timing resolutions of <1.6 ns. All crystals of 0.4 × 0.4 × 20 mm3 and 0.3 × 0.3 × 20 mm3 could be clearly resolved if the crystal array was 1 mm smaller in the four sides than that in the SiPM array. CONCLUSIONS High DOI resolution PET detectors were developed using both GAGG and LYSO arrays with crystal sizes of 0.3 and 0.4 mm, respectively, and a length of 20 mm. The detectors can be used in the future to develop small animal PET scanners, especially dedicated mouse imaging PET scanners, which can simultaneously achieve high sensitivity and ultra-high spatial resolution. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Ming Niu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Zheng Liu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Zhonghua Kuang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Xiaohui Wang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ning Ren
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ziru Sang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - San Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Longhan Cong
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Tao Sun
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Zhanli Hu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Yongfeng Yang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
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Kuang Z, Wang X, Ren N, Wu S, Zeng T, Niu M, Cong L, Sang Z, Liu Z, Sun T, Hu Z, Liang D, Liu X, Zheng H, Yang Y. Physical and Imaging Performance of SIAT aPET under Different Energy Windows and Timing Windows. Med Phys 2022; 49:1432-1444. [PMID: 35049067 DOI: 10.1002/mp.15455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 12/20/2021] [Accepted: 12/22/2021] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The performance of small animal PET scanners depends on the energy window (EW) and timing window (TW). In NEMA Standards Publication NU 4-2008, detailed procedures of the performance measurements are defined, but the EW and TW are not specified. In this work, the effects of EW and TW on the physical and imaging performance of SIAT aPET will be evaluated. METHODS First, the flood histogram, energy resolution and timing resolution were measured for a detector of SIAT aPET. Second, the spatial resolutions were measured with different EWs. Third, the sensitivities, the scatter fractions (SFs), and noise equivalent count rates (NECRs) of a mouse-sized phantom and a rat-sized phantom, the recovery coefficients (RCs) of rods of different sizes, and the percentage standard deviation (%STD) of the NEMA image quality phantom were measured for different EWs and TWs. Last, images of a hot rod phantom, a mouse heart and a rat brain were acquired from the scanner with different EWs. RESULTS The SIAT aPET detectors provided good flood histograms such that all but the corner crystals can be resolved even with lower energies of 250-350 keV, an average energy resolution of 21.1±1.9 % and an average timing resolution of 2.63±0.69 ns. The average spatial resolutions obtained with EWs of 250-350 keV and 450-550 keV are 0.68 mm and 0.75 mm. For EWs of 250-750 keV, 350-750 keV, and 450-750 keV with a fixed TW of 12 ns, the sensitivities at center of field of view are 16.0%, 11.9%, and 8.2%, the peak NECRs of a mouse-sized phantom are 355.6 kcps, 324.4 kcps, and 249.4 kcps, and the peak NECRs of a rat-sized phantom are 148.5 kcps, 144.3 kcps, and 117.7 kcps, respectively. For the TWs of 4 ns, 8 ns,12 ns, and 20 ns with a fixed EW of 350-750 keV, the sensitivities at center of field of view are 9.6%, 11.4%, 11.9%, and 12.2%, the peak NECRs of a mouse-sized phantom are 260.1 kcps, 311.5 kcps, 324.4 kcps and 324.9 kcps, and the peak NECRs of a rat-sized phantom are 110.5 kcps, 137.3 kcps,144.3 kcps and 142.6 kcps, respectively. Narrowing the EW and TW improves the RCs of rods of all sizes, and the %STD of images obtained with different EWs and TWs are similar. Rods with diameter down to 0.8 mm can be visually resolved from images of the hot rod phantom obtained with different EWs. Images of mouse heart with high spatial resolution and rat brain with detail brain structure were obtained with different EWs. Images of both phantom and in-vivo animals obtained with different EWs only showed subtle difference. CONCLUSION The performance of SIAT aPET under different EWs and TWs was compared. The EW and TW affect the sensitivity, SF, and NECR, but not the spatial resolution and animal images of SIAT aPET, which imply that careful optimization of the EW and TW is not required. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Zhonghua Kuang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Xiaohui Wang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ning Ren
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - San Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Tianyi Zeng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ming Niu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Longhan Cong
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ziru Sang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Zheng Liu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Tao Sun
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Zhanli Hu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Dong Liang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Xin Liu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Hairong Zheng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Yongfeng Yang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
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Mohammadi A, Inadama N, Nishikido F, Yamaya T. Development of dual-ended depth-of-interaction detectors using laser-induced crystals for small animal PET systems. Phys Med Biol 2021; 66. [PMID: 34325418 DOI: 10.1088/1361-6560/ac18fc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 07/29/2021] [Indexed: 11/11/2022]
Abstract
Sensitivity and spatial resolution of positron emission tomography (PET) scanners can be improved by using thicker scintillation crystals with depth-of-interaction (DOI) encoding. Subsurface laser engraving (SSLE) can be used to segment crystals of a scintillation detector in order to fabricate a DOI detector. We previously applied SSLE to crystal bars of 3 × 3 × 20 mm3and 1.5 × 1.5 × 20 mm3and developed two dual-ended detectors with DOI segments of 3 mm and 1.5 mm, respectively. To further improve the DOI resolution, our SSLE detector design can be used with smaller pitch crystal bars, making them excellent detector candidates for small animal PET scanners with submillimetre resolution. In the present study, three small crystal bars of 1 × 1 × 20 mm3, 2 × 1 × 20 mm3, and 2 × 1 × 40 mm3were laser engraved to 12, 20 and 40 segments, respectively, by applying SSLE in their height directions. The segmented crystal bars were characterised in three prototype detector arrangements. First, the 1 × 1 × 20 mm3crystal bars were characterised in an 8 × 8 crystal array designed for DOI encoding along crystal height in a conventional small animal PET design. Second, a 4 × 8 crystal array of 2 × 1 × 20 mm3crystal bars was characterised for using the DOI information for crystal interaction positioning along the axial axis of a small animal PET scanner. Finally, the third part of the study was performed on a single 2 × 1 × 40 mm3crystal bar with 40 segments to investigate the feasibility of DOI estimation in longer crystals for application in a system with extended axial length. We evaluated the capability of segment identification and energy resolution of theses detectors. The 3D position maps of the detectors were obtained using the Anger-type calculation and the crystal identification performance was evaluated for each detector. Clear segment separation was obtained for the crystal arrays with 12 (segment pitch of 1.67 mm) and 20 (segment pitch of 1 mm) segments. Mean energy resolutions of 8.8% ± 0.4% and 9.6% ± 0.8% at 511 keV were obtained for the segments in the central regions of the 8 × 8 array with 12 segments and the 4 × 8 array with 20 segments, respectively. Clear segment identification was found to be difficult for the detector with 40 segments, especially for the segments at the middle of the crystal. Energy and interaction positioning characterisation results suggest that both prototype detectors with 12 and 20 segments are well suited for small animal PET scanners with high spatial resolution.
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Affiliation(s)
- Akram Mohammadi
- Institute of Quantum Medical Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Naoko Inadama
- Institute of Quantum Medical Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Fumihiko Nishikido
- Institute of Quantum Medical Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Taiga Yamaya
- Institute of Quantum Medical Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
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Huang HM. Monte Carlo evaluation of a LYSO-based Compton camera using two origin ensemble algorithms with resolution recovery. Med Phys 2021; 48:5300-5310. [PMID: 34260083 DOI: 10.1002/mp.15092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 06/23/2021] [Accepted: 07/04/2021] [Indexed: 11/05/2022] Open
Abstract
PURPOSE Due to the lack of depth-of-interaction information, a Compton camera made of lutetium-yttrium orthosilicate (LYSO) crystals suffers from poor spatial resolution, which may lead to an unreliable range verification in proton therapy. The aim of this study is to evaluate the performance of a LYSO-based Compton camera using the origin ensemble algorithm with resolution recovery (OE-RR). We also proposed a regularized version of OE-RR called ROE-RR. METHODS We simulated a two-layer LYSO-based Compton camera which was used to detect prompt gammas (PGs) produced by a proton beam irradiated on a water phantom. PG images reconstructed by the OE-RR algorithm were evaluated and compared with those reconstructed by the proposed ROE-RR algorithm. RESULTS Our simulated results show that both the OE-RR and ROE-RR algorithms could provide an accurate estimate of the Bragg peak position, with a mean positioning error of 2.5 mm. Compared to the OE-RR algorithm, the proposed ROE-RR algorithm is less sensitive with respect to initial conditions and requires less iterations for converging to equilibrium. More importantly, the proposed ROE-RR algorithm could provide better image quality than the OE-RR algorithm, especially in low-count data. CONCLUSIONS For LYSO-based Compton cameras, using a resolution-recovery image reconstruction algorithm is essential for reliable range verification.
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Affiliation(s)
- Hsuan-Ming Huang
- Institute of Medical Device and Imaging, College of Medicine, National Taiwan University, Taipei City, Taiwan
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11
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Evaluation of high-resolution and depth-encoding PET detector modules based on single-ended readout with TOFPET2 ASIC. RADIATION DETECTION TECHNOLOGY AND METHODS 2021. [DOI: 10.1007/s41605-021-00270-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Zhang X, Yu H, Xie Q, Xie S, Ye B, Guo M, Zhao Z, Huang Q, Xu J, Peng Q. Design study of a PET detector with 0.5 mm crystal pitch for high-resolution preclinical imaging. Phys Med Biol 2021; 66. [PMID: 34130263 DOI: 10.1088/1361-6560/ac0b82] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 06/15/2021] [Indexed: 11/12/2022]
Abstract
Preclinical positron emission tomography (PET) is a sensitive and quantitative molecule imaging modality widely used in characterizing the biological processes and diseases in small animals. The purpose of this study is to investigate the methods to optimize a PET detector for high-resolution preclinical imaging. The PET detector proposed in this study consists of a 28 × 28 array of LYSO crystals 0.5 × 0.5 × 6.25 mm3in size, a wedged lightguide, and a 6 × 6 array of SiPMs 3 × 3 mm2in size. The simulation results showed that the most uniform flood map was achieved when the thickness of the lightguide was 2.35 mm. The quality of the flood map was significantly improved by suppressing the electronics noises using the simple threshold method with a best threshold. The peak-to-valley ratio of flood map improved 25.4% when the algorithm of ICS rejection was applied. An energy resolution (12.96% ± 1.03%) was measured on the prototype scanner constructed with 12 proposed detectors. Lastly, a prototype preclinic PET imager was constructed with 12 optimized detectors. The point source experiment was performed and an excellent spatial resolution (axial: 0.56 mm, tangential: 0.46 mm, radial: 0.42 mm) was achieved with the proposed high-performance PET detectors.
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Affiliation(s)
- Xi Zhang
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Hongsen Yu
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Qiangqiang Xie
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Siwei Xie
- Institute of Biomedical Engineering Shenzhen Bay Laboratory, Shenzhen, 518132, People's Republic of China
| | - Baihezi Ye
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Minghao Guo
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, People's Republic of China
| | - Zhixiang Zhao
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, People's Republic of China
| | - Qiu Huang
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, People's Republic of China
| | - Jianfeng Xu
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Qiyu Peng
- Institute of Biomedical Engineering Shenzhen Bay Laboratory, Shenzhen, 518132, People's Republic of China
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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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14
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Behnamian H, Yousefnejad S, Shafiee M, Rafiei A. Study of two-layer tapered depth of interaction PET detector. Appl Radiat Isot 2021; 174:109731. [PMID: 33964523 DOI: 10.1016/j.apradiso.2021.109731] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 04/05/2021] [Accepted: 04/09/2021] [Indexed: 10/21/2022]
Abstract
Improving detection efficiency in small animal PET scanners without degrading spatial resolution is one of the main problems of these scanners. Commercial small animal PET scanners use different methods to achieve desirable levels of sensitivity and spatial resolution. GE Healthcare eXplore VISTA PET scanner uses double layer (LYSO-GSO) depth-of-interaction (DOI) capable cuboid detector modules. In this work, the design of GE Healthcare eXplore VISTA PET scanner is improved using tapered detector geometry instead of cuboid geometry. Using tapered detector geometry, the gaps between adjacent modules are filled and the sensitive volume has increased about 11.5%. The new designed PET scanner sensitivity and spatial resolution are studied for different crystal layer configurations (LYSO-GSO and GSO-LYSO with different thicknesses). As expected, average sensitivity over FOV is improved. Spatial resolution is slightly degraded but it is still uniform over FOV.
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Affiliation(s)
- Hadi Behnamian
- Department of Physics, University of Guelph, 50 Stone Road East, Guelph, Ontario, Canada.
| | - Sirous Yousefnejad
- Iranian Light Source Facility, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran.
| | - Mehdi Shafiee
- Energetic Cosmos Laboratory, Nazarbayev University, Astana, Kazakhstan.
| | - Alireza Rafiei
- Department of Energy Engineering, Sharif University of Technology, Tehran, Iran.
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15
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LaBella A, Cao X, Zeng X, Zhao W, Goldan AH. Sub-2 mm depth of interaction localization in PET detectors with prismatoid light guide arrays and single-ended readout using convolutional neural networks. Med Phys 2021; 48:1019-1025. [PMID: 33305482 PMCID: PMC11025679 DOI: 10.1002/mp.14654] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/30/2020] [Accepted: 11/13/2020] [Indexed: 11/11/2022] Open
Abstract
PURPOSE Depth of interaction (DOI) readout in PET imaging has been researched in efforts to mitigate parallax error, which would enable the development of small diameter, high-resolution PET scanners. However, DOI PET has not yet been commercialized due to the lack of practical, cost-effective, and data efficient DOI readout methods. The rationale for this study was to develop a supervised machine learning algorithm for DOI estimation in PET that can be trained and deployed on unique sets of crystals. METHODS Depth collimated flood data was experimentally acquired using a Na-22 source with a depth-encoding single-ended readout Prism-PET module consisting of lutetium yttrium orthosilicate (LYSO) crystals coupled 4-to-1 to 3×3 mm 2 silicon photomultiplier (SiPM) pixels on one end and a segmented prismatoid light guide array on the other end. A convolutional neural network (CNN) was trained to perform DOI estimation on data from center, edge and corner crystals in the Prism-PET module using (a) all non-zero readout pixels and (b) only the 4 highest readout signals per event. CNN testing was performed on data from crystals not included in CNN training. RESULTS An average DOI resolution of 1.84 mm full width at half maximum (FWHM) across all crystals was achieved when using all readout signals per event with the CNN compared to 3.04 mm FWHM DOI resolution using classical estimation. When using only the 4 highest signals per event, an average DOI resolution of 1.92 mm FWHM was achieved, representing only a 4% dropoff in CNN performance compared to using all non-zero pixels per event. CONCLUSIONS Our CNN-based DOI estimation algorithm provides the best reported DOI resolution in a single-ended readout module and can be readily deployed on crystals not used for model training.
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Affiliation(s)
- Andy LaBella
- Department of Radiology, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, USA
| | - Xinjie Cao
- Department of Electrical and Computer Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY, USA
| | - Xinjie Zeng
- Department of Electrical and Computer Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY, USA
| | - Wei Zhao
- Department of Radiology, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, USA
| | - Amir H. Goldan
- Department of Radiology, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, USA
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Zeng T, Gao J, Gao D, Kuang Z, Sang Z, Wang X, Hu L, Chen Q, Chu X, Liang D, Liu X, Yang Y, Zheng H, Hu Z. A GPU-accelerated fully 3D OSEM image reconstruction for a high-resolution small animal PET scanner using dual-ended readout detectors. ACTA ACUST UNITED AC 2020; 65:245007. [DOI: 10.1088/1361-6560/aba6f9] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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17
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Kuang Z, Wang X, Ren N, Wu S, Gao J, Zeng T, Gao D, Zhang C, Sang Z, Hu Z, Du J, Liang D, Liu X, Zheng H, Yang Y. Design and performance of SIAT aPET: a uniform high-resolution small animal PET scanner using dual-ended readout detectors. Phys Med Biol 2020; 65:235013. [PMID: 32992302 DOI: 10.1088/1361-6560/abbc83] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In this work, a small animal PET scanner named SIAT aPET was developed using dual-ended readout depth encoding detectors to simultaneously achieve high spatial resolution and high sensitivity. The scanner consists of four detector rings with 12 detector modules per ring; the ring diameter is 111 mm and the axial field of view (FOV) is 105.6 mm. The images are reconstructed using an ordered subset expectation maximization (OSEM) algorithm. The spatial resolution of the scanner was measured by using a 22Na point source at the center axial FOV with different radial offsets. The sensitivity of the scanner was measured at center axis of the scanner with different axial positions. The count rate performance of the system was evaluated by scanning mouse-sized and rat-sized phantoms. An ultra-micro hot-rods phantom and two mice injected with 18F-NaF and 18F-FDG were scanned on the scanner. An average depth of interaction (DOI) resolution of 1.96 mm, energy resolution of 19.1% and timing resolution of 1.20 ns were obtained for the detector. Average spatial resolutions of 0.82 mm and 1.16 mm were obtained up to a distance of 30 mm radially from the center of the FOV when reconstructing a point source in 1% and 10% warm backgrounds, respectively, using OSEM reconstruction with 16 subsets and 10 iterations. Sensitivities of 16.0% and 11.9% were achieved at center of the scanner for energy windows of 250-750 keV and 350-750 keV respectively. Peak noise equivalent count rates (NECRs) of 324 kcps and 144 kcps were obtained at an activity of 26.4 MBq for the mouse-sized and rat-sized phantoms. Rods of 1.0 mm diameter can be visually resolved from the image of the ultra-micro hot-rods phantom. The capability of the scanner was demonstrated by high quality in-vivo mouse images.
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Affiliation(s)
- Zhonghua Kuang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China. Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China. Authors have contributed equally to this work
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18
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Li M, Wang Y, Abbaszadeh S. Development and initial characterization of a high-resolution PET detector module with DOI. Biomed Phys Eng Express 2020; 6:065020. [PMID: 34234961 PMCID: PMC8260077 DOI: 10.1088/2057-1976/abbd4f] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Organ-dedicated PET scanners are becoming more prevalent because of their advantages in higher sensitivity, improved image quality, and lower cost. Detectors utilized in these scanners have finer pixel size with depth of interaction (DOI) capability. This work presents a LYSO(Ce) detector module with DOI capability which has the potential to be scaled up to a high-resolution small animal or organ-dedicated PET system. For DOI capability, a submodule with one LYSO block detector utilizing PETsys TOFPET2 application-specific integrated circuit (ASIC) was previously developed in our lab. We scaled up the submodule and optimized the configuration to allow for a compact housing of the dual-readout boards in one side of the blocks by designing a high-speed dual-readout cable to maintain the original pin-to-pin relationship between the Samtec connectors. The module size is 53.8 × 57.8 mm2. Each module has 2 × 2 LYSO blocks, each LYSO block consists of 4 × 4 LYSO units, and each LYSO unit contains a 6 × 6 array of 1 × 1 × 20 mm3 LYSO crystals. The four lateral surfaces of LYSO crystal were mechanically ground to W14, and the two end surfaces were polished. Two ends of the LYSO crystal are optically connected to SiPM for DOI measurement. Eight LYSO blocks performance including energy, timing, and DOI resolution is characterized with a single LYSO slab. The in-panel and orthogonal-panel spatial resolution of the two modules with 107.4 mm distance between each other are measured at 9 positions within the field of view (FOV) with a 22Na source. Results show that the average energy, timing, and DOI resolution of all LYSO blocks are 16.13% ± 1.01% at 511 keV, 658.03 ± 15.18 ps, and 2.62 ± 0.06 mm, respectively. The energy and timing resolution of two modules are 16.35% and 0.86 ns, respectively. The in-panel and orthogonal-panel spatial resolution of the two modules at the FOV center are 1.9 and 4.4 mm respectively.
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Affiliation(s)
- Mohan Li
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, United States of America
| | - Yuli Wang
- Department of Electrical and Computer Engineering, University of California, Santa Cruz, Santa Cruz, 95064, United States of America
| | - Shiva Abbaszadeh
- Department of Electrical and Computer Engineering, University of California, Santa Cruz, Santa Cruz, 95064, United States of America
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19
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Park H, Lee JS. SiPM signal readout for inter-crystal scatter event identification in PET detectors. Phys Med Biol 2020; 65:205010. [PMID: 32702670 DOI: 10.1088/1361-6560/aba8b4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In positron emission tomography (PET) with pixelated detectors, a significant number of annihilation photons interact with scintillation crystals through single or multiple Compton scattering events. When these partial energy depositions occur across multiple crystal elements, we call them inter-crystal scatter (ICS) events. ICS events lead to incorrect localization of the annihilation photons, thereby degrading the PET image contrast, spatial resolution, and lesion detectability. The accurate identification of ICS events is the first essential step to improve the quality of PET images by rejecting ICS events or recovering ICS events without losing PET sensitivity. In this study, we propose a novel silicon photomultiplier (SiPM) readout method to identify ICS events in one-to-one coupled PET detectors with a reduced number of data acquisition channels. For concept verification, we assembled a PET detector that consists of a 16-channel SiPM array and 4 [Formula: see text] 4 lutetium oxyorthosilicate (LSO) array with a 3.2 mm crystal pitch. The proposed SiPM readout scheme serializes the 16 SiPM anode signals into four pulse train outputs encoded with four increasing time-delays in steps of 250 ns intervals. A Sum signal of the 16 SiPM anodes provides the timing information for time-of-flight measurement and a trigger signal for coincidence detection. A time-over-threshold (TOT) method was applied for obtaining the energy information followed by a subsequent TOT-to-energy calibration. We successfully identified the ICS events and determined their interacted positions and deposited energies by analyzing the digital pulses from the four pulse train output channels. The occurrence rate of ICS events was 10.85% for the 4 × 4 PET detector module with 3.2 mm-pitch LSO crystals. The PET detector yielded an energy resolution of 10.9 [Formula: see text] 0.6% and coincidence timing resolution of 285 [Formula: see text] 12 ps FWHM. We expect that the proposed method can be a useful solution for alleviating the readout burden of SiPM-based PET scanners with ICS event identification capability.
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Affiliation(s)
- Haewook Park
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Republic of Korea. Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul 03080, Republic of Korea
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Sanaat A, Arabi H, Reza Ay M, Zaidi H. Novel preclinical PET geometrical concept using a monolithic scintillator crystal offering concurrent enhancement in spatial resolution and detection sensitivity: a simulation study. ACTA ACUST UNITED AC 2020; 65:045013. [DOI: 10.1088/1361-6560/ab63ef] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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21
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Guo L, Tian J, Chen P, Derenzo S, Choong WS. Improving timing performance of double-ended readout in TOF-PET detectors. JOURNAL OF INSTRUMENTATION : AN IOP AND SISSA JOURNAL 2020; 15:P01003. [PMID: 33273960 PMCID: PMC7710007 DOI: 10.1088/1748-0221/15/01/p01003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Scintillation crystals of 20mm length or longer are needed for clinical time-of-flight positron emission tomography (TOF-PET) to ensure effective detection efficiency for gamma photons. However, the use of long crystals would deteriorate the key performance of TOF-PET detectors, time and spatial resolution, because of the variations in the travel times of the photons in crystals and the effects of parallax errors. In this work, we studied double-ended readout TOF-PET detectors based on coupling a long scintillation crystal to SiPMs at both ends for correcting the depth-dependent effects to improve the coincidence time resolution (CTR). In particular, we focused our attention to analyze timing performance using different correction methods, including trigger times of the individual photodetectors at both ends of the crystal, the simple average of the trigger times, and the weighted average based on the inverse variances of the depth-dependent corrected trigger times. For a 3 mm × 3 mm × 25mm unpolished lutetium fine silicate (LFS) crystal with double-ended readout and practical head-on irradiation, a CTR of 246ps FWHM can be achieved using depth-dependent timing-correction and weighted average time method compared to 280ps FWHM using the conventional simple average time method and 393ps FWHM using the conventional single-ended readout. The results show that the depth-dependent timing-correction and weighted average time method in double-ended readout can effectively correct for the trigger time variations in TOF-PET detector utilizing long unpolished crystals, resulting in an improvement in the CTR of as much as 37% compared to single-ended readout.
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Affiliation(s)
- L. Guo
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, U.S.A
- Key Laboratory of Ultra-fast photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, No. 17 Xinxi Road, Xi’an 710119, China
- College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, No. 19 Yuquan Road, Beijing 100049, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China
| | - J. Tian
- Key Laboratory of Ultra-fast photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, No. 17 Xinxi Road, Xi’an 710119, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China
| | - P. Chen
- Key Laboratory of Ultra-fast photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, No. 17 Xinxi Road, Xi’an 710119, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China
| | - S.E. Derenzo
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, U.S.A
| | - W.-S. Choong
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, U.S.A
- Corresponding author.
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22
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Li M, Abbaszadeh S. Depth-of-interaction study of a dual-readout detector based on TOFPET2 application-specific integrated circuit. Phys Med Biol 2019; 64:175008. [PMID: 31382253 DOI: 10.1088/1361-6560/ab3866] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Depth-of-interaction (DOI) capability is important for achieving high spatial resolution and sensitivity in dedicated organ and small animal positron emission tomography (PET) scanners. The dual-ended readout is one of the common methods that can achieve good DOI resolution. The aim of this study is to evaluate a dual-ended readout detector based on silicon photomultiplier (SiPM) and TOFPET2 application-specific integrated circuit (ASIC). The detector is based on 4 [Formula: see text] 4 lutetium-yttrium oxyorthosilicate (LYSO) units, each unit contained 6 [Formula: see text] 6 LYSO crystals, and the crystal size was 1 [Formula: see text] 1 [Formula: see text] 20 mm3. The four lateral surfaces of LYSO crystals were mechanically ground to W14 (surface roughness 10-14 [Formula: see text]m), and the two ended surfaces were polished (surface roughness <0.5 [Formula: see text]m). The reflector was Toray Lumirror E60, and the packing fraction of the LYSO block was 86.5%. Each LYSO unit was read out from both ends with two Hamamatsu S13361-3050AE-08 SiPM arrays. The analog output signals of SiPM were digitized by PETsys TOFPET2 ASIC and acquired by PETsys SiPM Readout System. The ASIC and SiPM were cooled by a fan and a Peltier element. To investigate the crystal resolvability, different light guide thicknesses including 0.8, 1, 1.2 and 2 mm were tested. The light guide was made of optical glass (H-K9L-Foctek Photoincs), and the size and refractive index were 6.45 [Formula: see text] 6.45 mm2 and 1.53 (at 420 nm), respectively. To characterize the detector performance at different depths, another 1 [Formula: see text] 25.8 [Formula: see text] 20 mm3 single LYSO slab was used. Data were acquired at 10 depths (1, 3, …, 19 mm), and each depth had a 10 min acquisition time and about 40 thousand coincidence events. During the experiment, the SiPM temperature was controlled as 27.6 [Formula: see text] 0.4 °C. The results showed that the 1.2 mm light guide offered the best crystal resolvability. The energy, coincidence time, and DOI resolution full-width at half-maximum of the detector were characterized as 15.66% [Formula: see text] 0.66%, 602.98 [Formula: see text] 10.58 ps, and 2.33 [Formula: see text] 0.07 mm, respectively. The good DOI resolution indicates the potential of utilizing the detector for high-resolution PET applications.
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Affiliation(s)
- Mohan Li
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
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Zhao Z, Xie S, Zhang X, Yang J, Huang Q, Xu J, Peng Q. An Advanced 100-Channel Readout System for Nuclear Imaging. IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2019; 68:3200-3210. [PMID: 31413382 PMCID: PMC6693670 DOI: 10.1109/tim.2018.2877952] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Reading out from large-scale silicon photomultiplier (SiPM) arrays is a fundamental technical obstacle blocking the application of revolutionary SiPM technologies in nuclear imaging systems. Typically, it requires using dedicated application-specific integrated circuits (ASICs) that need a long iterative process, special expertise, and tools to develop. The pico-positron emission tomography (Pico-PET) electronics system is an advanced 100-channel readout system based on 1-bit sigma-delta modulation and a field-programmable gate array (FPGA). It is compact (6 × 6 × 0.8 cm3 in size), consumes little power (less than 3W), and is constructed with off-the-shelf low-cost components. In experimental studies, the Pico-PET system demonstrates excellent and consistent performance. In addition, it has some unique features that are essential for nuclear imaging systems, such as its ability to measure V-I curves, breakdown voltages, and the dark currents of 100 SiPMs accurately, simultaneously, and in real time. The flexibility afforded by FPGAs allows multiple-channel clustering and intelligent triggering for different detector designs. These highly sought-after features are not offered by any other ASICs and electronics systems developed for nuclear imaging. We conclude that the Pico-PET electronics system provides a practical solution to the long-standing bottleneck problem that has limited the development of potentially advanced nuclear imaging technology using SiPMs.
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Affiliation(s)
- Zhixiang Zhao
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200025, China
| | - Siwei Xie
- State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Xi Zhang
- State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jingwu Yang
- State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Qiu Huang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200025, China
| | - Jianfeng Xu
- State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Qiyu Peng
- Department of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
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Du J, Bai X, Cherry SR. Performance comparison of depth-encoding detectors based on dual-ended readout and different SiPMs for high-resolution PET applications. Phys Med Biol 2019; 64:15NT03. [PMID: 31018180 DOI: 10.1088/1361-6560/ab1c37] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Silicon photomultipliers (SiPMs) are widely used in positron emission tomography (PET), however, SiPMs from different vendors vary in their performance characteristics. In addition, the specifications provided by the manufacturers are measured under different operating conditions and using different test setups, making it difficult to choose the optimal device for a specific application using the published specifications. In this work, we evaluated four state-of-the-art 8 × 8 arrays of ~3 × 3 mm2 SiPMs from SensL, KETEK, and Hamamatsu for high-resolution dual-ended readout detectors using the same experimental setup and procedures. The results showed that all four SiPM arrays are excellent candidates for high-resolution PET applications, although some interesting differences in performance were noted.
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Affiliation(s)
- Junwei Du
- Author to whom any correspondence should be addressed
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25
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Abstract
In most high-resolution PET detector designs, there is an inherent trade-off between spatial resolution and detector efficiency. We have developed and tested a new geometry for the detector module which avoids this trade-off. The module uses a layered structure, in which four crystal slabs are stacked in the depth direction and optically separated by enhanced specular reflector (ESR) film. The scintillation light within each layer is measured by 16 SiPMs located on the four sides of the crystal. Analog signals from all SiPMs (4 × 16) on the four sides of the crystal are digitized individually using a 64-channel TOFPET-2 module. The four-sided readout method reduces the problem of light trapping resulting from total internal reflection when reading out the end(s) of traditional scintillation crystal arrays, thus increasing the light collection efficiency. In this work, we demonstrate the readout of a complete layered detector with 4 layers. The high light collection efficiency results in a FWHM energy resolution of 10.3%, and a FWHM timing resolution of 348 ps. The distribution of scintillation light detected by the SiPMs was used to decode the interaction position of each gamma ray using a trained neural network. A FWHM spatial resolution of 1.1 ± 0.1 mm was achieved. This design allows the detection efficiency of the module to be increased by adding additional crystal slabs along the depth direction. Since the position, energy, and timing are measured for each layer independently, increasing the system sensitivity by adding more layers will not affect the spatial/energy/timing resolution. Furthermore, the layered structure allows partial recovery of position information for events that undergo Compton scatter within the detector.
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Affiliation(s)
- Peng Peng
- Author to whom any correspondence should be addressed
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26
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Kuang Z, Yang Q, Wang X, Fu X, Ren N, Wu S, Zhang C, Zhao B, Sang Z, Hu Z, Du J, Liang D, Liu X, Zheng H, Yang Y. Performance of a depth encoding PET detector module using light sharing and single-ended readout with SiPMs. ACTA ACUST UNITED AC 2019; 64:085012. [DOI: 10.1088/1361-6560/ab1152] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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27
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Fujibuchi T, Toyoda T, Terasaki K. Measurement of basic characteristics of scintillation-type radiation survey meters with multi-pixel photon counter. Appl Radiat Isot 2018; 140:12-17. [PMID: 29936270 DOI: 10.1016/j.apradiso.2018.06.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Revised: 06/06/2018] [Accepted: 06/11/2018] [Indexed: 11/30/2022]
Abstract
The basic characteristics of three low-cost radiation survey meters using multi-pixel photon counters (MPPC), the C12137, T-GMK2-S, and iMetry, were measured. The linearity of the dose rate was confirmed over the full range of each instrument. All the survey meters could obtain gamma-ray energy spectra, with an accuracy within ± 30% of the theoretical value. These survey meters are therefore applicable for radiation management.
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Affiliation(s)
- Toshioh Fujibuchi
- Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, Japan.
| | - Takatoshi Toyoda
- Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, Japan
| | - Kento Terasaki
- Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, Japan
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28
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Xu J, Sun Q, Wu Z, Guo L, Xie S, Huang Q, Peng Q. Development of broad-band high-reflectivity multilayer film for positron emission tomography system. JOURNAL OF INSTRUMENTATION : AN IOP AND SISSA JOURNAL 2018; 13:P09016. [PMID: 33828611 PMCID: PMC8022915 DOI: 10.1088/1748-0221/13/09/p09016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The use of non-ideal reflective materials and low-precision manual manufacturing technologies is a fundamental technical obstacle blocking the positron emission tomography (PET) systems from achieving better performances. We propose to address that long-standing obstacle with advanced multilayer dielectric coating technologies. We designed an broad-band multilayer high-reflectivity (HR) film that can be coated directly on the surface of ultra-precision polished lutetiumyttrium oxyorthosilicate (LYSO) scintillators. The film consists of 48 layers of TiO2/SiO2/HfO2 which are deposited on LYSO scintillator crystal alternately using the electron beam evaporation method. The overall thickness of the HR film is about 3μm. The HR film combines 3 quarter wavelength reflective films, with the central wavelengths of 365 nm, 430 nm and 570 nm respectively, to match the emission spectrum of the LYSO scintillator. The optical experimental results show that the HR film achieved an excellent average reflectivity of 99.50% at 8° incident angle for incident lights with wavelengths between 360 to 620 nm. The average reflectivity at 60° incident angle is higher than 90%. The results of the hardness experiments and the adhesive strength experiments show that the HR film has an excellent mechanical strength. The HR coating technology developed in this study is very attractive because it allows to "print" high-performance reflectors on a scintillator directly with high-precision, instead of manually gluing reflective films on the scintillator. Thus, we conclude that the HR film provides a viable solution to the long standing technical bottleneck that limits the development of high-performance detectors for advanced PET imaging.
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Affiliation(s)
- J Xu
- The State Key Lab of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, 430074, China
| | | | - Z Wu
- The State Key Lab of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, 430074, China
| | | | - S Xie
- The State Key Lab of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, 430074, China
| | - Q Huang
- School of Biomedical Engineering, Shanghai Jiaotong University, Shanghai, 200030, China
| | - Q Peng
- Department of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A
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