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Park H, Yi M, Lee JS. Silicon photomultiplier signal readout and multiplexing techniques for positron emission tomography: a review. Biomed Eng Lett 2022; 12:263-283. [PMID: 35892029 PMCID: PMC9308856 DOI: 10.1007/s13534-022-00234-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/21/2022] [Accepted: 05/30/2022] [Indexed: 12/03/2022] Open
Abstract
In recent years, silicon photomultiplier (SiPM) is replacing the photomultiplier tube (PMT) in positron emission tomography (PET) systems due to its superior properties, such as fast single-photon timing response, small gap between adjacent photosensitive pixels in the array, and insensitivity to magnetic fields. One of the technical challenges when developing SiPM-based PET systems or other position-sensitive radiation detectors is the large number of output channels coming from the SiPM array. Therefore, various signal multiplexing methods have been proposed to reduce the number of output channels and the load on the subsequent data acquisition (DAQ) system. However, the large PN-junction capacitance and quenching resistance of the SiPM yield undesirable resistance–capacitance delay when multiple SiPMs are combined, which subsequently causes the accumulation of dark counts and signal fluctuation of SiPMs. Therefore, without proper SiPM signal handling and processing, the SiPMs may yield worse timing characteristics than the PMTs. This article reviews the evolution of signal readout and multiplexing methods for the SiPM. In this review, we focus primarily on analog electronics for SiPM signal multiplexing, which allows for the reduction of DAQ channels required for the SiPM-based position-sensitive detectors used in PET and other radiation detector systems. Although the applications of most technologies described in the article are not limited to PET systems, the review highlights efforts to improve the physical performance (e.g. spatial, energy, and timing resolutions) of PET detectors and systems.
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Affiliation(s)
- Haewook Park
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080 South Korea
- Department of Nuclear Medicine, Seoul National University College of Medicine, 101, Daehak-ro, Jongno-gu, Seoul, 03080 South Korea
| | - Minseok Yi
- Department of Nuclear Medicine, Seoul National University College of Medicine, 101, Daehak-ro, Jongno-gu, Seoul, 03080 South Korea
- Interdisciplinary Program in Bioengineering, Seoul National University College of Engineering, Seoul, 03080 South Korea
- Integrated Major in Innovative Medical Science, Seoul National University College of Engineering, Seoul, 03080 South Korea
| | - Jae Sung Lee
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080 South Korea
- Department of Nuclear Medicine, Seoul National University College of Medicine, 101, Daehak-ro, Jongno-gu, Seoul, 03080 South Korea
- Interdisciplinary Program in Bioengineering, Seoul National University College of Engineering, Seoul, 03080 South Korea
- Integrated Major in Innovative Medical Science, Seoul National University College of Engineering, Seoul, 03080 South Korea
- Brightonix Imaging Inc, Seoul, 04782 South Korea
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Gong Y, Shan H, Teng Y, Tu N, Li M, Liang G, Wang G, Wang S. Parameter-Transferred Wasserstein Generative Adversarial Network (PT-WGAN) for Low-Dose PET Image Denoising. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2021; 5:213-223. [PMID: 35402757 PMCID: PMC8993163 DOI: 10.1109/trpms.2020.3025071] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Due to the widespread use of positron emission tomography (PET) in clinical practice, the potential risk of PET-associated radiation dose to patients needs to be minimized. However, with the reduction in the radiation dose, the resultant images may suffer from noise and artifacts that compromise diagnostic performance. In this paper, we propose a parameter-transferred Wasserstein generative adversarial network (PT-WGAN) for low-dose PET image denoising. The contributions of this paper are twofold: i) a PT-WGAN framework is designed to denoise low-dose PET images without compromising structural details, and ii) a task-specific initialization based on transfer learning is developed to train PT-WGAN using trainable parameters transferred from a pretrained model, which significantly improves the training efficiency of PT-WGAN. The experimental results on clinical data show that the proposed network can suppress image noise more effectively while preserving better image fidelity than recently published state-of-the-art methods. We make our code available at https://github.com/90n9-yu/PT-WGAN.
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Affiliation(s)
- Yu Gong
- College of Medicine and Biological Information Engineering, Northeastern University, Shenyang 110169, China, and Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Hongming Shan
- Institute of Science and Technology for Brain-inspired Intelligence, Fudan University, Shanghai 200433, China, and the Shanghai Center for Brain Science and Brain-Inspired Technology, Shanghai 201210, China
| | - Yueyang Teng
- College of Medicine and Biological Information Engineering, Northeastern University, Shenyang 110169, China, and the Key Laboratory of Intelligent Computing in Medical Images, Ministry of Education, Shenyang 110169, China
| | - Ning Tu
- PET-CT/MRI Center and Molecular Imaging Center, Wuhan University Renmin Hospital, Wuhan, 430060, China
| | - Ming Li
- Neusoft Medical Systems Co., Ltd, Shenyang 110167, China
| | - Guodong Liang
- Neusoft Medical Systems Co., Ltd, Shenyang 110167, China
| | - Ge Wang
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 USA
| | - Shanshan Wang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
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Raylman RR, Ledden P, Stolin AV, Hou B, Jaliparthi G, Martone PF. Small animal, positron emission tomography-magnetic resonance imaging system based on a clinical magnetic resonance imaging scanner: evaluation of basic imaging performance. J Med Imaging (Bellingham) 2018; 5:033504. [PMID: 30840723 DOI: 10.1117/1.jmi.5.3.033504] [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: 05/14/2018] [Accepted: 08/14/2018] [Indexed: 11/14/2022] Open
Abstract
Development of advanced preclinical imaging techniques has had an important impact on the field of biomedical research, with positron emission tomography (PET) imaging the most mature of these efforts. Developers of preclinical PET scanners have joined the recent multimodality imaging trend by combining PET imaging with other modalities, such as magnetic resonance imaging (MRI). Our group has developed a combined PET-MRI insert for the imaging of animals up to the size of rats in a clinical 3T MRI scanner. The system utilizes a sequential scanner configuration instead of the more common coplanar geometry. The PET component of the system consists of a ring of 12 liquid-cooled, SiPM-based detector modules ( diameter = 15.2 cm ). System performance was evaluated with the NEMA NU 4-2008 protocol. Spatial resolution is ∼ 1.71 mm 5 cm from the center of the field-of-view measured from single-slice rebinned filtered backprojection-reconstructed images. Peak noise equivalent count rate is 17.7 kcps at 8.5 MBq; peak sensitivity is 2.9%. The MRI component of the system is composed of a 12-cm-diameter birdcage transmit/receive coil with a dual-preamplifier interface possessing very low noise preamplifiers. System performance was evaluated using American College of Radiology-based methods. Image homogeneity is 99%; the ghosting ratio is 0.0054. The signal-to-noise ratio is 95 and spatial resolution is ∼ 0.25 mm . There was no discernable cross-modality interference.
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Affiliation(s)
- Raymond R Raylman
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
| | - Patrick Ledden
- Nova Medical Inc., Wilmington, Massachusetts, United States
| | - Alexander V Stolin
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
| | - Bob Hou
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
| | - Ganghadar Jaliparthi
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
| | - Peter F Martone
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
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Sajedi S, Zeraatkar N, Taheri M, Kaviani S, Khanmohammadi H, Sarkar S, Sabet H, Ay MR. Generic high resolution PET detector block using 12 × 12 SiPM array. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aaade8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Surti S, Karp JS. Impact of event positioning algorithm on performance of a whole-body PET scanner using one-to-one coupled detectors. Phys Med Biol 2018; 63:055008. [PMID: 29411709 DOI: 10.1088/1361-6560/aaad76] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The advent of silicon photomultipliers (SiPMs) has introduced the possibility of increased detector performance in commercial whole-body PET scanners. The primary advantage of these photodetectors is the ability to couple a single SiPM channel directly to a single pixel of PET scintillator that is typically 4 mm wide (one-to-one coupled detector design). We performed simulation studies to evaluate the impact of three different event positioning algorithms in such detectors: (i) a weighted energy centroid positioning (Anger logic), (ii) identifying the crystal with maximum energy deposition (1st max crystal), and (iii) identifying the crystal with the second highest energy deposition (2nd max crystal). Detector simulations performed with LSO crystals indicate reduced positioning errors when using the 2nd max crystal positioning algorithm. These studies are performed over a range of crystal cross-sections varying from 1 × 1 mm2 to 4 × 4 mm2 as well as crystal thickness of 1 cm to 3 cm. System simulations were performed for a whole-body PET scanner (85 cm ring diameter) with a long axial FOV (70 cm long) and show an improvement in reconstructed spatial resolution for a point source when using the 2nd max crystal positioning algorithm. Finally, we observe a 30-40% gain in contrast recovery coefficient values for 1 and 0.5 cm diameter spheres when using the 2nd max crystal positioning algorithm compared to the 1st max crystal positioning algorithm. These results show that there is an advantage to implementing the 2nd max crystal positioning algorithm in a new generation of PET scanners using one-to-one coupled detector design with lutetium based crystals, including LSO, LYSO or scintillators that have similar density and effective atomic number as LSO.
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Affiliation(s)
- S Surti
- Department of Radiology, The University of Pennsylvania, Philadelphia, PA 19104, United States of America
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Calva-Coraza E, Alva-Sánchez H, Murrieta-Rodríguez T, Martínez-Dávalos A, Rodríguez-Villafuerte M. Optimization of a large-area detector-block based on SiPM and pixelated LYSO crystal arrays. Phys Med 2017; 42:19-27. [PMID: 29173915 DOI: 10.1016/j.ejmp.2017.08.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Revised: 08/02/2017] [Accepted: 08/03/2017] [Indexed: 10/19/2022] Open
Abstract
We present the performance evaluation of a large-area detector module based on the ArrayC-60035-64P, an 8×8 array of tileable, 7.2mm pitch, silicon photomultipliers (SiPM) by SensL, covering a total area of 57.4mm×57.4mm. We characterized the ArrayC-60035-64P, operating at room temperature, using LYSO pixelated crystal arrays of different pitch sizes (1.075, 1.430, 1.683, 2.080 and 2.280mm) to determine the resolvable crystal size. After an optimization process, a 7mm thick coupling light guide was used for all crystal pitches. To identify the interaction position a 16-channel (8 columns, 8 rows) symmetric charge division (SCD) readout board together with a center-of-gravity algorithm was used. Based on this, we assembled the detector modules using a 40×40 LYSO, 1.43mm pitch array, covering the total detector area. Calibration was performed using a 137Cs source resulting in excellent crystal maps with minor geometric distortion, a mean 4.1 peak-to-valley ratio and 9.6% mean energy resolution for 662keV photons in the central region. The resolvability index was calculated in the x and y directions with values under 0.42 in all cases. We show that these large area SiPM arrays, combined with a 16-channel SCD readout board, can offer high spatial resolution, without processing a big number of signals, attaining excellent energy resolution and detector uniformity.
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Affiliation(s)
- E Calva-Coraza
- Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, 01000, Mexico City, Mexico
| | - H Alva-Sánchez
- Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, 01000, Mexico City, Mexico.
| | - T Murrieta-Rodríguez
- Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, 01000, Mexico City, Mexico
| | - A Martínez-Dávalos
- Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, 01000, Mexico City, Mexico
| | - M Rodríguez-Villafuerte
- Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, 01000, Mexico City, Mexico
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Zhang J, Moore ME, Wang Z, Rong Z, Yang C, Hayward JP. Study of sampling rate influence on neutron-gamma discrimination with stilbene coupled to a silicon photomultiplier. Appl Radiat Isot 2017; 128:120-124. [PMID: 28709029 DOI: 10.1016/j.apradiso.2017.06.036] [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] [Received: 01/25/2017] [Revised: 06/21/2017] [Accepted: 06/22/2017] [Indexed: 10/19/2022]
Abstract
Choosing a digitizer with an appropriate sampling rate is often a trade-off between performance and economy. The influence of sampling rates on the neutron-gamma Pulse Shape Discrimination (PSD) with a solid stilbene scintillator coupled to a Silicon Photomultiplier was investigated in this work. Sampling rates from 125MSPS to 2GSPS from a 10-bit digitizer were used to collect detector pulses produced by the interactions of a Cf-252 source. Due to the decreased signal-to-noise ratio (SNR), the PSD performance degraded with reduced sampling rates. The reason of PSD performance degradation was discussed. Then, an efficient combination of filtering and digital signal processing (DSP) was then applied to suppress the timing noise and electronic background noise. The results demonstrate an improved PSD performance especially at low sampling rates, down to 125MSPS. Using filtering and DSP, the ascribed Figure of Merit (FOM) at 125keVee (± 10keVee) increased from 0.95 to 1.02 at 125MSPS. At 300keVee and above, all the FOMs are better than 2.00. Our study suggests that 250MSPS is a good enough sampling rate for neutron-gamma discrimination in this system in order to be sensitive to neutrons at and above ~ 125keVee.
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Affiliation(s)
- Jinglong Zhang
- College of Physical Science and Technology, Key Laboratory of Radiation Physics and Technology, Ministry of Education, Sichuan University, Chengdu 610065, China
| | - Michael E Moore
- Department of Nuclear Engineering, The University of Tennessee, Knoxville, TN, United States
| | - Zhonghai Wang
- College of Physical Science and Technology, Key Laboratory of Radiation Physics and Technology, Ministry of Education, Sichuan University, Chengdu 610065, China
| | - Zhou Rong
- College of Physical Science and Technology, Key Laboratory of Radiation Physics and Technology, Ministry of Education, Sichuan University, Chengdu 610065, China.
| | - Chaowen Yang
- College of Physical Science and Technology, Key Laboratory of Radiation Physics and Technology, Ministry of Education, Sichuan University, Chengdu 610065, China
| | - Jason P Hayward
- Department of Nuclear Engineering, The University of Tennessee, Knoxville, TN, United States
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Stolin AV, Martone PF, Jaliparthi G, Raylman RR. Preclinical positron emission tomography scanner based on a monolithic annulus of scintillator: initial design study. J Med Imaging (Bellingham) 2017; 4:011007. [PMID: 28097210 DOI: 10.1117/1.jmi.4.1.011007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 12/06/2016] [Indexed: 02/02/2023] Open
Abstract
Positron emission tomography (PET) scanners designed for imaging of small animals have transformed translational research by reducing the necessity to invasively monitor physiology and disease progression. Virtually all of these scanners are based on the use of pixelated detector modules arranged in rings. This design, while generally successful, has some limitations. Specifically, use of discrete detector modules to construct PET scanners reduces detection sensitivity and can introduce artifacts in reconstructed images, requiring the use of correction methods. To address these challenges, and facilitate measurement of photon depth-of-interaction in the detector, we investigated a small animal PET scanner (called AnnPET) based on a monolithic annulus of scintillator. The scanner was created by placing 12 flat facets around the outer surface of the scintillator to accommodate placement of silicon photomultiplier arrays. Its performance characteristics were explored using Monte Carlo simulations and sections of the NEMA NU4-2008 protocol. Results from this study revealed that AnnPET's reconstructed spatial resolution is predicted to be [Formula: see text] full width at half maximum in the radial, tangential, and axial directions. Peak detection sensitivity is predicted to be 10.1%. Images of simulated phantoms (mini-hot rod and mouse whole body) yielded promising results, indicating the potential of this system for enhancing PET imaging of small animals.
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Affiliation(s)
- Alexander V Stolin
- West Virginia University , Center for Advanced Imaging, Department of Radiology, One Medical Center Dr., Box 9236, Morgantown, West Virginia 26506, United States
| | - Peter F Martone
- West Virginia University , Center for Advanced Imaging, Department of Radiology, One Medical Center Dr., Box 9236, Morgantown, West Virginia 26506, United States
| | - Gangadhar Jaliparthi
- West Virginia University , Center for Advanced Imaging, Department of Radiology, One Medical Center Dr., Box 9236, Morgantown, West Virginia 26506, United States
| | - Raymond R Raylman
- West Virginia University , Center for Advanced Imaging, Department of Radiology, One Medical Center Dr., Box 9236, Morgantown, West Virginia 26506, United States
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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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Raylman R, Stolin A. Immersion cooling of silicon photomultipliers (SiPM) for nuclear medicine imaging applications. RADIAT MEAS 2016. [DOI: 10.1016/j.radmeas.2015.12.043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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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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Freese DL, Vandenbroucke A, Innes D, Lau FWY, Hsu DFC, Reynolds PD, Levin CS. Thermal regulation of tightly packed solid-state photodetectors in a 1 mm(3) resolution clinical PET system. Med Phys 2015; 42:305-13. [PMID: 25563270 DOI: 10.1118/1.4903889] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Silicon photodetectors are of significant interest for use in positron emission tomography (PET) systems due to their compact size, insensitivity to magnetic fields, and high quantum efficiency. However, one of their main disadvantages is fluctuations in temperature cause strong shifts in gain of the devices. PET system designs with high photodetector density suffer both increased thermal density and constrained options for thermally regulating the devices. This paper proposes a method of thermally regulating densely packed silicon photodetectors in the context of a 1 mm(3) resolution, high-sensitivity PET camera dedicated to breast imaging. METHODS The PET camera under construction consists of 2304 units, each containing two 8 × 8 arrays of 1 mm(3) LYSO crystals coupled to two position sensitive avalanche photodiodes (PSAPD). A subsection of the proposed camera with 512 PSAPDs has been constructed. The proposed thermal regulation design uses water-cooled heat sinks, thermoelectric elements, and thermistors to measure and regulate the temperature of the PSAPDs in a novel manner. Active cooling elements, placed at the edge of the detector stack due to limited access, are controlled based on collective leakage current and temperature measurements in order to keep all the PSAPDs at a consistent temperature. This thermal regulation design is characterized for the temperature profile across the camera and for the time required for cooling changes to propagate across the camera. These properties guide the implementation of a software-based, cascaded proportional-integral-derivative control loop that controls the current through the Peltier elements by monitoring thermistor temperature and leakage current. The stability of leakage current, temperature within the system using this control loop is tested over a period of 14 h. The energy resolution is then measured over a period of 8.66 h. Finally, the consistency of PSAPD gain between independent operations of the camera over 10 days is tested. RESULTS The PET camera maintains a temperature of 18.00 ± 0.05 °C over the course of 12 h while the ambient temperature varied 0.61 °C, from 22.83 to 23.44 °C. The 511 keV photopeak energy resolution over a period of 8.66 h is measured to be 11.3% FWHM with a maximum photopeak fluctuation of 4 keV. Between measurements of PSAPD gain separated by at least 2 day, the maximum photopeak shift was 6 keV. CONCLUSIONS The proposed thermal regulation scheme for tightly packed silicon photodetectors provides for stable operation of the constructed subsection of a PET camera over long durations of time. The energy resolution of the system is not degraded despite shifts in ambient temperature and photodetector heat generation. The thermal regulation scheme also provides a consistent operating environment between separate runs of the camera over different days. Inter-run consistency allows for reuse of system calibration parameters from study to study, reducing the time required to calibrate the system and hence to obtain a reconstructed image.
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Affiliation(s)
- D L Freese
- Departments of Electrical Engineering, Radiology, Physics, and BioEngineering, Stanford University, Stanford, California 94305-5128
| | - A Vandenbroucke
- Departments of Electrical Engineering, Radiology, Physics, and BioEngineering, Stanford University, Stanford, California 94305-5128
| | - D Innes
- Departments of Electrical Engineering, Radiology, Physics, and BioEngineering, Stanford University, Stanford, California 94305-5128
| | - F W Y Lau
- Departments of Electrical Engineering, Radiology, Physics, and BioEngineering, Stanford University, Stanford, California 94305-5128
| | - D F C Hsu
- Departments of Electrical Engineering, Radiology, Physics, and BioEngineering, Stanford University, Stanford, California 94305-5128
| | - P D Reynolds
- Departments of Electrical Engineering, Radiology, Physics, and BioEngineering, Stanford University, Stanford, California 94305-5128
| | - Craig S Levin
- Departments of Electrical Engineering, Radiology, Physics, and BioEngineering, Stanford University, Stanford, California 94305-5128
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Grkovski M, Brzezinski K, Cindro V, Clinthorne NH, Kagan H, Lacasta C, Mikuž M, Solaz C, Studen A, Weilhammer P, Žontar D. Evaluation of a high resolution silicon PET insert module. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION A, ACCELERATORS, SPECTROMETERS, DETECTORS AND ASSOCIATED EQUIPMENT 2015; 788:86-94. [PMID: 33173251 PMCID: PMC7650022 DOI: 10.1016/j.nima.2015.03.078] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Conventional PET systems can be augmented with additional detectors placed in close proximity of the region of interest. We developed a high resolution PET insert module to evaluate the added benefit of such a combination. The insert module consists of two back-to-back 1 mm thick silicon sensors, each segmented into 1040 1 mm2 pads arranged in a 40 by 26 array. A set of 16 VATAGP7.1 ASICs and a custom assembled data acquisition board were used to read out the signal from the insert module. Data were acquired in slice (2D) geometry with a Jaszczak phantom (rod diameters of 1.2-4.8 mm) filled with 18F-FDG and the images were reconstructed with ML-EM method. Both data with full and limited angular coverage from the insert module were considered and three types of coincidence events were combined. The ratio of high-resolution data that substantially improves quality of the reconstructed image for the region near the surface of the insert module was estimated to be about 4%. Results from our previous studies suggest that such ratio could be achieved at a moderate technological expense by using an equivalent of two insert modules (an effective sensor thickness of 4 mm).
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Affiliation(s)
- Milan Grkovski
- Jožef Stefan Institute, Ljubljana, Slovenia
- Memorial Sloan Kettering Cancer Center, New York, NY, USA
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