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Herweg K, Rutstrom D, Nadig V, Stand L, Melcher CL, Zhuravleva M, Schulz V, Gundacker S. Timing limits of ultrafast cross-luminescence emission in CsZnCl-based crystals for TOF-CT and TOF-PET. EJNMMI Phys 2024; 11:59. [PMID: 38977509 DOI: 10.1186/s40658-024-00663-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 06/27/2024] [Indexed: 07/10/2024] Open
Abstract
BACKGROUND Good timing resolution in medical imaging applications such as TOF-CT or TOF-PET can boost image quality or patient comfort significantly by reducing the influence of background noise. However, the timing resolution of state-of-the-art detectors in CT and PET are limited by their light emission process. Core-valence cross-luminescence is an alternative, but well-known compounds (e.g. BaF2) pose several problems for medical imaging applications, such as their emission wavelength in the deep UV. CsZnCl-based materials show promise to solve this issue, as they provide fast decay times of 1-2 ns and an emission wavelength around 300 nm. RESULTS In this work, we investigated two CsZnCl-compounds: Cs2ZnCl4 and Cs3ZnCl5. We validated the previously published decay times on a time-correlated single-photon counting setup with 1.786 ± 0.016 ns for Cs2ZnCl4 and 1.034 ± 0.013 ns for Cs3ZnCl5. The setup's high resolution enabled the discovery of an additional prompt emission component with a significant abundance of 98 ± 18 (Cs2ZnCl4) and 86 ± 14 (Cs3ZnCl5) photons/MeV energy deposit. In a PET coincidence experiment, we measured the best coincidence time resolution (CTR) of 62 ps (FWHM) for Cs2ZnCL4 coupled to FBK VUV SiPMs with silicon oil. To assess the CTR for lower energies, we filtered the energy along the Compton continuum and found a deteriorated CTR that seems to be mainly influenced by photon statistics. Furthermore, this study gave us a rough estimate of e.g. 150 ps (FWHM) CTR at 100 keV energy for Cs2ZnCL4. From measurements with high activity of 14 MBq to check for pile-up effects we assume that Cs2ZnCl4 is better suited for high-rate time-of-flight applications than lutetium-based oxides. Simulations demonstrated that the stopping power of Cs2ZnCl4 is lower than for LSO:Ce,Ca, meaning that a high amount of material would be needed for TOF-PET applications. However, the stopping power seems acceptable for applications in TOF-CT. CONCLUSIONS The fast decay time, state-of-the-art CTR in benchtop experiments and high-rate suitability make CsZnCl materials a promising candidate for time-of-flight experiments. We consider especially TOF-CT a suitable application due to its relatively low X-ray energies (~ 100 keV) and the thusly acceptable stopping power of Cs2ZnCl4. Currently, further exploration of the prompt emission and its creation mechanism is planned, as well as investigating the light transport of Cs2ZnCl4 in longer crystals.
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Affiliation(s)
- Katrin Herweg
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany.
| | - Daniel Rutstrom
- Scintillation Materials Research Center, University of Tennessee Knoxville, Knoxville, TN, USA
- Department of Materials Science and Engineering, University of Tennessee Knoxville, Knoxville, TN, USA
| | - Vanessa Nadig
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Luis Stand
- Scintillation Materials Research Center, University of Tennessee Knoxville, Knoxville, TN, USA
- Department of Nuclear Engineering, University of Tennessee Knoxville, Knoxville, TN, USA
| | - Charles L Melcher
- Scintillation Materials Research Center, University of Tennessee Knoxville, Knoxville, TN, USA
- Department of Materials Science and Engineering, University of Tennessee Knoxville, Knoxville, TN, USA
- Department of Nuclear Engineering, University of Tennessee Knoxville, Knoxville, TN, USA
| | - Mariya Zhuravleva
- Scintillation Materials Research Center, University of Tennessee Knoxville, Knoxville, TN, USA
- Department of Materials Science and Engineering, University of Tennessee Knoxville, Knoxville, TN, USA
| | - Volkmar Schulz
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
- Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany
- Physics Institute III B, RWTH Aachen University, Aachen, Germany
| | - Stefan Gundacker
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany.
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Kuhl Y, Mueller F, Naunheim S, Bovelett M, Lambertus J, Schug D, Weissler B, Gegenmantel E, Gebhardt P, Schulz V. A finely segmented semi-monolithic detector tailored for high-resolution PET. Med Phys 2024; 51:3421-3436. [PMID: 38214395 DOI: 10.1002/mp.16928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 12/20/2023] [Accepted: 12/20/2023] [Indexed: 01/13/2024] Open
Abstract
BACKGROUND Preclinical research and organ-dedicated applications use and require high (spatial-)resolution positron emission tomography (PET) detectors to visualize small structures (early) and understand biological processes at a finer level of detail. Researchers seeking to improve detector and image spatial resolution have explored various detector designs. Current commercial high-resolution systems often employ finely pixelated or monolithic scintillators, each with its limitations. PURPOSE We present a semi-monolithic detector, tailored for high-resolution PET applications with a spatial resolution in the range of 1 mm or better, merging concepts of monolithic and pixelated crystals. The detector features LYSO slabs measuring (24 × 10 × 1) mm3, coupled to a 12 × 12 readout channel photosensor with 4 mm pitch. The slabs are grouped in two arrays of 44 slabs each to achieve a higher optical photon density despite the fine segmentation. METHODS We employ a fan beam collimator for fast calibration to train machine-learning-based positioning models for all three dimensions, including slab identification and depth-of-interaction (DOI), utilizing gradient tree boosting (GTB). The data for all dimensions was acquired in less than 2 h. Energy calculation was based on a position-dependent energy calibration. Using an analytical timing calibration, time skews were corrected for coincidence timing resolution (CTR) estimation. RESULTS Leveraging machine-learning-based calibration in all three dimensions, we achieved high detector spatial resolution: down to 1.18 mm full width at half maximum (FWHM) detector spatial resolution and 0.75 mm mean absolute error (MAE) in the planar-monolithic direction, and 2.14 mm FWHM and 1.03 mm MAE for DOI at an energy window of (435-585) keV. Correct slab interaction identification in planar-segmented direction exceeded 80%, alongside an energy resolution of 12.7% and a CTR of 450 ps FWHM. CONCLUSIONS The introduced finely segmented, high-resolution slab detector demonstrates appealing performance characteristics suitable for high-resolution PET applications. The current benchtop-based detector calibration routine allows these detectors to be used in PET systems.
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Affiliation(s)
- Yannick Kuhl
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Florian Mueller
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Stephan Naunheim
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Matthias Bovelett
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Janko Lambertus
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - David Schug
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
- Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany
| | - Bjoern Weissler
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
- Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany
| | | | - Pierre Gebhardt
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Volkmar Schulz
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
- Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany
- Physics Institute III B, RWTH Aachen University, Aachen, Germany
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Nadig V, Hornisch M, Oehm J, Herweg K, Schulz V, Gundacker S. 16-channel SiPM high-frequency readout with time-over-threshold discrimination for ultrafast time-of-flight applications. EJNMMI Phys 2023; 10:76. [PMID: 38044383 PMCID: PMC10694125 DOI: 10.1186/s40658-023-00594-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 11/20/2023] [Indexed: 12/05/2023] Open
Abstract
BACKGROUND Over the past five years, ultrafast high-frequency (HF) readout concepts have advanced the timing performance of silicon photomultipliers (SiPMs). The shown impact in time-of-flight (TOF) techniques can further push the limits in light detection and ranging (LiDAR), time-of-flight positron-emission tomography (TOF-PET), time-of-flight computed tomography (TOF-CT) or high-energy physics (HEP). However, upscaling these electronics to a system-applicable, multi-channel readout, has remained a challenging task, posed by the use of discrete components and a high power consumption. To this day, there are no means to exploit the high TOF resolution of these electronics on system scale or to measure the actual timing performance limits of a full detector block. METHODS In this work, we present a 16-channel HF readout board, including leading-edge discrimination and a linearized time-over-threshold (TOT) method, which is fully compatible with a high-precision time-to-digital converters (TDCs), such as the picoTDC developed at CERN. The discrete implementation allows ideal adaptation of this readout to a broad range of detection tasks. As a first step, the functionality of the circuit has been tested using the TOFPET2 ASIC as back-end electronics to emulate the TDC, also in view of its properties as a highly scalable data acquisition solution. RESULTS The produced board is able to mitigate influences of baseline shifts in the TOFPET2 front end, which has been shown in experiments with a pulsed laser, increasing the achievable intrinsic coincidence timing resolution (CTR) of the TOFPET2 readout electronics from 70 ps (FWHM) to 62 ps (FWHM). Single-channel coincidence experiments including a [Formula: see text]-source, 2[Formula: see text]2[Formula: see text]3 mm[Formula: see text] LYSO:Ce,Ca crystals and Broadcom NUV-MT SiPMs resulted in a CTR of 118 ps (FWHM). For a 4[Formula: see text]4 matrix of 3.88[Formula: see text]3.88[Formula: see text]19 mm[Formula: see text] LYSO:Ce,Ca crystals one-to-one coupled to a 4[Formula: see text]4 array of Broadcom NUV-MT SiPMs, an average CTR of 223 ps (FWHM) was obtained. CONCLUSION The implemented 16-channel HF electronics are fully functionall and have a negligible influence on the timing performance of the back-end electronics used, here the TOFPET2 ASIC. The ongoing integration of the picoTDC with the 16-channel HF board is expected to further set the path toward sub-100 ps TOF-PET and sub-30ps TOF resolution for single-photon detection.
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Affiliation(s)
- Vanessa Nadig
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Forckenbeckstraße 55, 52074, Aachen, Germany
| | - Matthias Hornisch
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Forckenbeckstraße 55, 52074, Aachen, Germany
| | - Jakob Oehm
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Forckenbeckstraße 55, 52074, Aachen, Germany
| | - Katrin Herweg
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Forckenbeckstraße 55, 52074, Aachen, Germany
| | - Volkmar Schulz
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Forckenbeckstraße 55, 52074, Aachen, Germany
- Hyperion Hybrid Imaging Systems GmbH, Pauwelsstraße 19, 52074, Aachen, Germany
- III. Physikalisches Institut B, RWTH Aachen University, Otto-Blumenthal-Straße, 52074, Aachen, Germany
- Fraunhofer Institute for Digital Medicine MEVIS, Forckenbeckstraße 55, 52074, Aachen, Germany
| | - Stefan Gundacker
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Forckenbeckstraße 55, 52074, Aachen, Germany.
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Li Y, LaBella A, Zeng X, Wang Z, Petersen E, Cao X, Zhao W, Goldan AH. Interleaved signal multiplexing readout in depth encoding Prism-PET detectors. Med Phys 2023; 50:4234-4243. [PMID: 37191309 PMCID: PMC11057968 DOI: 10.1002/mp.16456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 03/01/2023] [Accepted: 03/29/2023] [Indexed: 05/17/2023] Open
Abstract
BACKGROUND Given the large number of readout pixels in clinical positron emission tomography (PET) scanners, signal multiplexing is an indispensable feature to reduce scanner complexity, power consumption, heat output, and cost. PURPOSE In this paper, we introduce interleaved multiplexing (iMux) scheme that utilizes the characteristic light-sharing pattern of depth-encoding Prism-PET detector modules with single-ended readout. METHODS In the iMux readout, four anodes from every other silicon photomultiplier (SiPM) pixels across rows and columns, which overlap with four distinct light guides, are connected to the same application-specific integrated circuit (ASIC) channel. The 4-to-1 coupled Prism-PET detector module was used which consisted of a 16 × 16 array of 1.5 × 1.5 × 20 mm3 lutetium yttrium oxyorthosilicate (LYSO) scintillator crystals coupled to an 8 × 8 array with 3 × 3 mm2 SiPM pixels. A deep learning-based demultiplexing model was investigated to recover the encoded energy signals. Two different experiments were performed with non-multiplexed and multiplexed readouts to evaluate the spatial, depth of interaction (DOI), and timing resolutions of our proposed iMux scheme. RESULTS The measured flood histograms, using the decoded energy signals from our deep learning-based demultiplexing architecture, achieved perfect crystal identification of events with negligible decoding error. The average energy, DOI, and timing resolutions were 9.6 ± 1.5%, 2.9 ± 0.9 mm, and 266 ± 19 ps for non-multiplexed readout and 10.3 ± 1.6%, 2.8 ± 0.8 mm, and 311 ± 28 ps for multiplexed readout, respectively. CONCLUSIONS Our proposed iMux scheme improves on the already cost-effective and high-resolution Prism-PET detector module and provides 16-to-1 crystal-to-readout multiplexing without appreciable performance degradation. Also, only four SiPM pixels are shorted together in the 8 × 8 array to achieve 4-to-1 pixel-to-readout multiplexing, resulting in lower capacitance per multiplexed channel.
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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, US
| | - Andy LaBella
- Department of Radiology, Boston Children’s Hospital, Boston, MA, US
| | - Xinjie Zeng
- Department of Electrical and Computer Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY, US
| | - Zipai Wang
- Department of Biomedical Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY, US
| | - Eric Petersen
- Department of Biomedical Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY, US
| | - Xinjie Cao
- Department of Electrical and Computer Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY, US
| | - Wei Zhao
- Department of Radiology, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, US
| | - Amir H. Goldan
- Department of Radiology, Weill Cornell Medical College, Cornell University, New York, NY, US
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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] [Grants] [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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Du J, Jones T. Technical opportunities and challenges in developing total-body PET scanners for mice and rats. EJNMMI Phys 2023; 10:2. [PMID: 36592266 PMCID: PMC9807733 DOI: 10.1186/s40658-022-00523-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 12/20/2022] [Indexed: 01/03/2023] Open
Abstract
Positron emission tomography (PET) is the most sensitive in vivo molecular imaging technique available. Small animal PET has been widely used in studying pharmaceutical biodistribution and disease progression over time by imaging a wide range of biological processes. However, it remains true that almost all small animal PET studies using mouse or rat as preclinical models are either limited by the spatial resolution or the sensitivity (especially for dynamic studies), or both, reducing the quantitative accuracy and quantitative precision of the results. Total-body small animal PET scanners, which have axial lengths longer than the nose-to-anus length of the mouse/rat and can provide high sensitivity across the entire body of mouse/rat, can realize new opportunities for small animal PET. This article aims to discuss the technical opportunities and challenges in developing total-body small animal PET scanners for mice and rats.
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Affiliation(s)
- Junwei Du
- grid.27860.3b0000 0004 1936 9684Department of Biomedical Engineering, University of California at Davis, Davis, CA 95616 USA
| | - Terry Jones
- grid.27860.3b0000 0004 1936 9684Department of Radiology, University of California at Davis, Davis, CA 95616 USA
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Mueller F, Naunheim S, Kuhl Y, Schug D, Solf T, Schulz V. A semi-monolithic detector providing intrinsic DOI-encoding and sub-200 ps CRT TOF-capabilities for clinical PET applications. Med Phys 2022; 49:7469-7488. [PMID: 36259245 DOI: 10.1002/mp.16015] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 06/25/2022] [Accepted: 09/11/2022] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Current clinical positron emission tomography (PET) systems utilize detectors where the scintillator typically contains single elements of 3-6-mm width and about 20-mm height. While providing good time-of-flight performance, this design limits the spatial resolution and causes radial astigmatism as the depth-of-interaction (DOI) remains unknown. PURPOSE We propose an alternative, aiming to combine the advantages of current detectors with the DOI capabilities shown for monolithic concepts, based on semi-monolithic scintillators (slabs). Here, the optical photons spread along one dimension enabling DOI-encoding with a still small readout area beneficial for timing performance. METHODS An array of eight monolithic LYSO slabs of dimensions 3.9 × 32 × 19 mm3 was read out by a 64-channel photosensor containing digital SiPMs (DPC3200-22-44, Philips Digital Photon Counting). The position estimation in the detector's monolithic and DOI direction was based on a calibration with a fan beam collimator and the machine learning technique gradient tree boosting (GTB). RESULTS We achieved a positioning performance in terms of mean absolute error (MAE) of 1.44 mm for the monolithic direction and 2.12 mm for DOI considering a wide energy window of 300-700 keV. The energy resolution was determined to be 11.3%, applying a positional-dependent energy calibration. We established both an analytical and machine-learning-based timing calibration approach and applied them for a first-photon trigger. The analytical timing calibration corrects for electronic and optical time skews leading to 240 ps coincidence resolving time (CRT) for a pair of slab-detectors. The CRT was significantly improved by utilizing GTB to predict the time difference based on specific training data and applied on top of the analytical calibration. We achieved 209 ps for the wide energy window and 198 ps for a narrow selection around the photopeak (411-561 keV). To maintain the detector's sensitivity, no filters were applied to the data during processing. CONCLUSION Overall, the semi-monolithic detector provides attractive performance characteristics. Especially, a good CRT can be achieved while introducing DOI capabilities to the detector, making the concept suitable for clinical PET scanners.
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Affiliation(s)
- Florian Mueller
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Stephan Naunheim
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Yannick Kuhl
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - David Schug
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany.,Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany
| | - Torsten Solf
- Philips Digital Photon Counting (PDPC), Aachen, Germany
| | - Volkmar Schulz
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany.,Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany.,Fraunhofer Institute for Digital Medicine MEVIS, Aachen, Germany.,III. Institute of Physics B, RWTH Aachen University, Aachen, Germany
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Preliminary results of a single photon emission computed tomography (SPECT) detector for inspection of spent fuel assembly. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2022.110162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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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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Cao X, Labella A, Zeng X, Zhao W, Goldan AH. Depth of Interaction and Coincidence Time Resolution Characterization of Ultrahigh Resolution Time-of-Flight Prism-PET Modules. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2022. [DOI: 10.1109/trpms.2021.3110902] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Xinjie Cao
- Department of Eletrical and Computer Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Andy Labella
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Xinjie Zeng
- Department of Eletrical and Computer Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Wei Zhao
- Department of Radiology, Stony Brook University, Stony Brook, NY, USA
| | - Amir H. Goldan
- Department of Radiology, Stony Brook University, Stony Brook, NY, USA
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Sanchez D, Gomez S, Mauricio J, Freixas L, Sanuy A, Guixe G, Lopez A, Manera R, Marin J, Perez JM, Picatoste E, Pujol C, Sanmukh A, Rato P, Vela O, Gascon D. HRFlexToT: A High Dynamic Range ASIC for Time-of-Flight Positron Emission Tomography. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2022. [DOI: 10.1109/trpms.2021.3066426] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Yoshida E, Obata F, Kamada K, Yamaya T. A Crosshair Light Sharing PET Detector With DOI and TOF Capabilities Using Four-to-One Coupling and Single-Ended Readout. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2021. [DOI: 10.1109/trpms.2020.3032466] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Binder T, Kang HG, Nitta M, Schneider F, Yamaya T, Parodi K, Wiest F, Thirolf PG. Performance evaluation of a staggered three-layer DOI PET detector using a 1 mm LYSO pitch with PETsys TOFPET2 ASIC: comparison of HAMAMATSU and KETEK SiPMs. Phys Med Biol 2021; 66. [PMID: 33906179 DOI: 10.1088/1361-6560/abfbf3] [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: 10/12/2020] [Accepted: 04/27/2021] [Indexed: 11/11/2022]
Abstract
In this study, we propose a staggered three-layer depth-of-interaction (DOI) detector with a 1 mm crystal pitch and 19.8 mm total crystal thickness for a high-resolution and high-sensitivity small animal in-beam PET scanner. A three-layered stacked LYSO scintillation array (0.9 × 0.9 × 6.6 mm3crystals, 23 × 22 mm2surface area) read out by a SiPM array (8 × 8 channels, 3 × 3 mm2active area/channel and 50μm microcell size) with data acquisition, signal processing and digitization performed using the PETsys Electronics Evaluations kit (based on the TOFPET v2c ASIC) builds a DOI LYSO detector block. The performance of the DOI detector was evaluated in terms of crystal resolvability, energy resolution, and coincidence resolving time (CRT). A comparative performance evaluation of the staggered three-layer LYSO block was conducted with two different SiPM arrays from KETEK and HAMAMATSU. 100% (KETEK) and 99.8% (HAMAMATSU) of the crystals were identified, by using a flood irradiation the front- and back-side. The average energy resolutions for the 1st, 2nd, and 3rd layers were 16.5 (±2.3)%, 20.9(±4.0)%, and 32.7 (±21.0)% (KETEK) and 19.3 (±3.5)%, 21.2 (±4.1)%, and 26.6 (±10.3)% (HAMAMATSU) for the used SiPM arrays. The measured CRTs (FWHM) for the 1st, 2nd, and 3rd layers were 532 (±111) ps, 463 (±108) ps, and 447 (±111) ps (KETEK) and 402 (±46) ps, 392 (±54) ps, and 408 (±196) ps (HAMAMATSU). In conclusion, the performance of the staggered three-layer DOI detector with 1 mm LYSO pitch and 19.8 mm total crystal thickness was fully characterized. The feasibility of a highly performing readout of a high resolution DOI PET detector via SiPM arrays from KETEK and HAMAMATSU employing the PETsys TOFPET v2c ASIC could be demonstrated.
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Affiliation(s)
- Tim Binder
- Ludwig-Maximilians-Universität, Munich, Germany.,KETEK GmbH, Munich, Germany
| | - Han Gyu Kang
- Institute for Quantum Medical Science, National Institutes for Quantum and Radiological Science and Technology (QST), Chiba, Japan
| | | | | | - Taiga Yamaya
- Institute for Quantum Medical Science, National Institutes for Quantum and Radiological Science and Technology (QST), Chiba, Japan
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14
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Chaudhari AJ, Badawi RD. Application-specific nuclear medical in vivoimaging devices. Phys Med Biol 2021; 66. [PMID: 33770765 DOI: 10.1088/1361-6560/abf275] [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: 11/05/2019] [Accepted: 03/26/2021] [Indexed: 11/11/2022]
Abstract
Nuclear medical imaging devices, such as those enabling photon emission imaging (gamma camera, single photon emission computed tomography, or positron emission imaging), that are typically used in today's clinics are optimized for assessing large portions of the human body, and are classified as whole-body imaging systems. These systems have known limitations for organ imaging, therefore application-specific devices have been designed, constructed and evaluated. These devices, given their compact nature and superior technical characteristics, such as their higher detection sensitivity and spatial resolution for organ imaging compared to whole-body imaging systems, have shown promise for niche applications. Several of these devices have further been integrated with complementary anatomical imaging devices. The objectives of this review article are to (1) provide an overview of such application-specific nuclear imaging devices that were developed over the past two decades (in the twenty-first century), with emphasis on brain, cardiac, breast, and prostate imaging; and (2) discuss the rationale, advantages and challenges associated with the translation of these devices for routine clinical imaging. Finally, a perspective on the future prospects for application-specific devices is provided, which is that sustained effort is required both to overcome design limitations which impact their utility (where these exist) and to collect the data required to define their clinical value.
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Affiliation(s)
- Abhijit J Chaudhari
- Department of Radiology, University of California Davis, Sacramento, CA 95817, United States of America.,Center for Molecular and Genomic Imaging, University of California Davis, Davis, CA 95616, United States of America
| | - Ramsey D Badawi
- Department of Radiology, University of California Davis, Sacramento, CA 95817, United States of America.,Department of Biomedical Engineering, University of California Davis, Davis, CA 95616, United States of America
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15
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Nadig V, Schug D, Weissler B, Schulz V. Evaluation of the PETsys TOFPET2 ASIC in multi-channel coincidence experiments. EJNMMI Phys 2021; 8:30. [PMID: 33761038 PMCID: PMC7991069 DOI: 10.1186/s40658-021-00370-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 02/23/2021] [Indexed: 04/05/2023] Open
Abstract
BACKGROUND Aiming to measure the difference in arrival times of two coincident γ-photons with an accuracy in the order of 200ps, time-of-flight positron emission tomography systems commonly employ silicon photomultipliers (SiPMs) and high-resolution digitization electronics, application specific integrated circuits (ASICs). This work evaluates the performance of the TOFPET2 ASIC, released by PETsys Electronics S.A. in 2017, dependent on its configuration parameters in multi-channel coincidence measurements. METHODS SiPM arrays fabricated by different vendors (KETEK, SensL, Hamamatsu, Broadcom) were tested in combination with the ASIC. Scintillator arrays featuring different reflector designs and different configurations of the TOFPET2 ASIC software parameters were evaluated. The benchtop setup used is provided with the TOFPET2 ASIC evaluation kit by PETsys Electronics S.A. RESULTS Compared to existing studies featuring the TOFPET2 ASIC, multi-channel performance results dependent on a larger set of ASIC configuration parameters were obtained that have not been reported to this extend so far. The ASIC shows promising CRTs down to 219.9 ps in combination with two Hamamatsu S14161-3050-HS-08 SiPM arrays (128 channels read out, energy resolution 13.08%) and 216.1 ps in combination with two Broadcom AFBR-S4N44P643S SiPM arrays (32 channels read out, energy resolution 9.46%). The length of the trigger delay of the dark count suppression scheme has an impact on the ASIC performance and can be configured to further improve the coincidence resolution time. The integrator gain configuration has been investigated and allows an absolute improvement of the energy resolution by up to 1% at the cost of the linearity of the energy spectrum. CONCLUSION Measuring up to the time-of-flight performance of state-of-the-art positron emission tomography (ToF-PET) systems while providing a uniform and stable readout for multiple channels at the same time, the TOFPET2 ASIC is treated as promising candidate for the integration in future ToF-PET systems.
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Affiliation(s)
- Vanessa Nadig
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Pauwelsstrasse 17, Aachen, 52074 Germany
| | - David Schug
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Pauwelsstrasse 17, Aachen, 52074 Germany
- Hyperion Hybrid Imaging Systems GmbH, Pauwelsstrasse 19, Aachen, 52074 Germany
| | - Bjoern Weissler
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Pauwelsstrasse 17, Aachen, 52074 Germany
- Hyperion Hybrid Imaging Systems GmbH, Pauwelsstrasse 19, Aachen, 52074 Germany
| | - Volkmar Schulz
- Department of Physics of Molecular Imaging Systems, Experimental Molecular Imaging, RWTH Aachen University, Pauwelsstrasse 17, Aachen, 52074 Germany
- Hyperion Hybrid Imaging Systems GmbH, Pauwelsstrasse 19, Aachen, 52074 Germany
- III. Physikalisches Institut B, RWTH Aachen University, Otto-Blumenthal-Straße, Aachen, 52074 Germany
- Fraunhofer Institute for Digital Medicine MEVIS, Forckenbeckstrasse 55, Aachen, 52074 Germany
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16
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Yoshida E, Akamatsu G, Tashima H, Kamada K, Yoshikawa A, Yamaya T. First imaging demonstration of a crosshair light-sharing PET detector. Phys Med Biol 2021; 66:065013. [PMID: 33607635 DOI: 10.1088/1361-6560/abe839] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The crosshair light-sharing (CLS) PET detector is our original depth-of-interaction (DOI) detector, which is based on a single-ended readout scheme with quadrisected crystals comparable in size to a photo-sensor. In this work, we developed 32 CLS PET detectors, each of which consisted of a multi-pixel photon counter (MPPC) array and gadolinium fine aluminum garnet (GFAG) crystals, and we developed a benchtop prototype of a small animal size PET. Each GFAG crystal was 1.45 × 1.45 × 15 mm3. The MPPC had a surface area of 3.0 × 3.0 mm2. The benchtop prototype had two detector rings of 16 detector blocks. The ring diameter and axial field-of-view were 14.2 cm and 4.9 cm, respectively. The data acquisition system used was the PETsys silicon photomultiplier readout system. The continuous DOI information was binned into three DOI layers by applying a look-up-table to a 2D position histogram. Also, energy and timing information was corrected using DOI information. After the calibration procedure, the energy resolution and the coincidence time resolution were 14.6% and 531 ps, respectively. Imaging test results of a small rod phantom obtained by an iterative reconstruction method showed clear separation of 1.6 mm rods with the help of DOI information.
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Affiliation(s)
- Eiji Yoshida
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
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17
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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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18
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Ros A, Barrientos L, Borja-Lloret M, Casaña J, Muñoz E, Roser J, Udías J, Viegas R, Llosá G. New probe for the improvement of the Spatial Resolution in total-body PET (PROScRiPT). EPJ WEB OF CONFERENCES 2021. [DOI: 10.1051/epjconf/202125309004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In recent decades, PET scanners have been widely used for diagnosis and treatment monitoring in nuclear medicine. The continuous effort of the scientific community has led to improvements in scanner performance. Total-body PET is one of the latest upgrades in PET scanners. These kinds of scanners are able to scan the whole body of the patient with a single bed position, since the scanner tube is long enough for the patient to fit inside. While these scanners show unprecedented efficiency and extended field-of-view, a drawback is their low spatial resolution compared to dedicated scanners. In order to improve the spatial resolution of specific areas when measuring with a total-body PET scanner, the IRIS group at IFIC-Valencia is developing a probe. The proposed setup of the probe contains a monolithic scintillation crystal and a SiPM. The signal of the probe is read out by a TOFPET2 ASIC from PETsys, which has shown good performance for PET in terms of spatial and time resolutions. Furthermore, the PETsys technology generates a trigger signal that will be used to time synchronise the probe and the scanner. The proof-of-concept of the probe will be tested in a Preclinical Super Argus PET/CT scanner for small animals located at IFIC. Preliminary simulations of the scanner and the probe under ideal conditions show a slight improvement in the position reconstruction compared to the data obtained with the scanner, therefore we expect a considerable improvement when using the probe in a total-body PET scanner. Characterisation tests of the probe have been performed with a 22Na point-like source, obtaining an energy resolution of 9.09% for the 511 keV energy peak and a temporal resolution of 619 ps after time walk correction. The next step of the project is to test the probe measuring in temporal coincidence with the scanner.
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19
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LaBella A, Vaska P, Zhao W, Goldan AH. Convolutional Neural Network for Crystal Identification and Gamma Ray Localization in PET. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2020. [DOI: 10.1109/trpms.2020.2980985] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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20
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Nadig V, Weissler B, Radermacher H, Schulz V, Schug D. Investigation of the Power Consumption of the PETsys TOFPET2 ASIC. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2020. [DOI: 10.1109/trpms.2019.2955032] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Vanessa Nadig
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Bjoern Weissler
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Harald Radermacher
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Volkmar Schulz
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - David Schug
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
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21
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D'Ascenzo N, Antonecchia E, Gao M, Zhang X, Baumgartner G, Brensing A, Li Z, Liu Q, Rose G, Shi X, Zhang B, Kao CM, Ni J, Xie Q. Evaluation of a Digital Brain Positron Emission Tomography Scanner Based on the Plug&Imaging Sensor Technology. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2020. [DOI: 10.1109/trpms.2019.2937681] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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Moghadam N, Arpin L, Espagnet R, Bouchard J, Viscogliosi N, Lecomte R, Fontaine R. Performance investigation of LabPET II detector technology in an MRI-like environment. Phys Med Biol 2020; 65:035001. [PMID: 31726447 DOI: 10.1088/1361-6560/ab57e0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The EMI-compatibility of the LabPET II detection module (DM) to develop a high-resolution simultaneous PET/MRI system is investigated. The experimental set-up evaluates the performance of two LabPET II DMs in close proximity to RF coils excited at three different frequencies mimicking the electromagnetic environments of 3 T, 7 T, and 9.4 T MRI scanners. A gradient coil, with switching frequency from 10 kHz to 100 kHz, also surrounds one of the DMs to investigate the effects of the gradient field on the individual detector performance, such as the baseline of the DC-voltage and noise level along with both the energy and coincidence time resolutions. Measurements demonstrate a position shift of the energy photopeaks (⩽9%) and a slight deterioration of the energy and coincidence time resolutions in the presence of electromagnetic interferences from the gradient and RF coils. The electromagnetic interferences cause an average degradation of up to ~50% of the energy resolution (in time-over-threshold spectra) and up to 18% of the timing resolution. Based on these results, a modified version of the DM, including a composite shielding as well as an improved heat pipe-based cooling mechanism, capable of stabilizing the temperature of the DM at ~40 °C, is proposed and investigated. This shielded version shows no evidence of performance degradation inside an MRI-like environment. The experimental results demonstrate that a properly shielded version of the LabPET II DM is a viable candidate for an MR-compatible PET scanner.
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Affiliation(s)
- Narjes Moghadam
- Groupe de Recherche en Appareillage Médical de Sherbrooke (GRAMS), Department of Electrical and Computer Engineering, Interdisciplinary Institute for Technological Innovation (3IT), Université de Sherbrooke, Sherbrooke, Québec, Canada.,Author to whom any correspondence should be addressed
| | - Louis Arpin
- Imaging, Research and Technology (IR&T), Sherbrooke, Québec, Canada
| | - Romain Espagnet
- Groupe de Recherche en Appareillage Médical de Sherbrooke (GRAMS), Department of Electrical and Computer Engineering, Interdisciplinary Institute for Technological Innovation (3IT), Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Jonathan Bouchard
- Groupe de Recherche en Appareillage Médical de Sherbrooke (GRAMS), Department of Electrical and Computer Engineering, Interdisciplinary Institute for Technological Innovation (3IT), Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Nicolas Viscogliosi
- Groupe de Recherche en Appareillage Médical de Sherbrooke (GRAMS), Department of Electrical and Computer Engineering, Interdisciplinary Institute for Technological Innovation (3IT), Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Roger Lecomte
- Department of Nuclear Medicine and Radiobiology, Sherbrooke Molecular Imaging Center (CIMS), Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Réjean Fontaine
- Groupe de Recherche en Appareillage Médical de Sherbrooke (GRAMS), Department of Electrical and Computer Engineering, Interdisciplinary Institute for Technological Innovation (3IT), Université de Sherbrooke, Sherbrooke, Québec, Canada
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23
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Lamprou E, Gonzalez AJ, Sanchez F, Benlloch JM. Exploring TOF capabilities of PET detector blocks based on large monolithic crystals and analog SiPMs. Phys Med 2020; 70:10-18. [PMID: 31935602 PMCID: PMC7026714 DOI: 10.1016/j.ejmp.2019.12.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 11/08/2019] [Accepted: 12/04/2019] [Indexed: 12/01/2022] Open
Abstract
Monolithic scintillators are more frequently used in PET instrumentation due to their advantages in terms of accurate position estimation of the impinging gamma rays both planar and depth of interaction, their increased efficiency, and expected timing capabilities. Such timing performance has been studied when those blocks are coupled to digital photosensors showing an excellent timing resolution. In this work we study the timing behaviour of detectors composed by monolithic crystals and analog SiPMs read out by an ASIC. The scintillation light spreads across the crystal towards the photosensors, resulting in a high number of SiPMs and ASIC channels fired. This has been studied in relation with the Coincidence Timing Resolution (CTR). We have used LYSO monolithic blocks with dimensions of 50 × 50 × 15 mm3 coupled to SiPM arrays (8 × 8 elements with 6 × 6 mm2 area) which compose detectors suitable for clinical applications. While a CTR as good as 186 ps FWHM was achieved for a pair of 3 × 3 × 5 mm3 LYSO crystals, when using the monolithic block and the SiPM arrays, a raw CTR over 1 ns was observed. An optimal timestamp assignment was studied as well as compensation methods for the time-skew and time-walk errors. This work describes all steps followed to improve the CTR. Eventually, an average detector time resolution of 497 ps FWHM was measured for the whole thick monolithic block. This improves to 380 ps FWHM for a central volume of interest near the photosensors. The timing dependency with the photon depth of interaction and planar position are also included.
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Affiliation(s)
- Efthymios Lamprou
- Instituto de Instrumentación para Imagen Molecular (I3M), Centro Mixto CSIC - Universitat Politècnica de València, 46022 Valencia, Spain.
| | - Antonio J Gonzalez
- Instituto de Instrumentación para Imagen Molecular (I3M), Centro Mixto CSIC - Universitat Politècnica de València, 46022 Valencia, Spain
| | - Filomeno Sanchez
- Instituto de Instrumentación para Imagen Molecular (I3M), Centro Mixto CSIC - Universitat Politècnica de València, 46022 Valencia, Spain
| | - Jose M Benlloch
- Instituto de Instrumentación para Imagen Molecular (I3M), Centro Mixto CSIC - Universitat Politècnica de València, 46022 Valencia, Spain
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24
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Jiang W, Chalich Y, Deen MJ. Sensors for Positron Emission Tomography Applications. SENSORS 2019; 19:s19225019. [PMID: 31744258 PMCID: PMC6891456 DOI: 10.3390/s19225019] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 11/11/2019] [Accepted: 11/13/2019] [Indexed: 02/07/2023]
Abstract
Positron emission tomography (PET) imaging is an essential tool in clinical applications for the diagnosis of diseases due to its ability to acquire functional images to help differentiate between metabolic and biological activities at the molecular level. One key limiting factor in the development of efficient and accurate PET systems is the sensor technology in the PET detector. There are generally four types of sensor technologies employed: photomultiplier tubes (PMTs), avalanche photodiodes (APDs), silicon photomultipliers (SiPMs), and cadmium zinc telluride (CZT) detectors. PMTs were widely used for PET applications in the early days due to their excellent performance metrics of high gain, low noise, and fast timing. However, the fragility and bulkiness of the PMT glass tubes, high operating voltage, and sensitivity to magnetic fields ultimately limit this technology for future cost-effective and multi-modal systems. As a result, solid-state photodetectors like the APD, SiPM, and CZT detectors, and their applications for PET systems, have attracted lots of research interest, especially owing to the continual advancements in the semiconductor fabrication process. In this review, we study and discuss the operating principles, key performance parameters, and PET applications for each type of sensor technology with an emphasis on SiPM and CZT detectors—the two most promising types of sensors for future PET systems. We also present the sensor technologies used in commercially available state-of-the-art PET systems. Finally, the strengths and weaknesses of these four types of sensors are compared and the research challenges of SiPM and CZT detectors are discussed and summarized.
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Affiliation(s)
- Wei Jiang
- School of Biomedical Engineering, McMaster University, Hamilton, ON L8S 4L8, Canada;
| | - Yamn Chalich
- Department of Electrical and Computer Engineering, McMaster University, Hamilton, ON L8S 4L8, Canada;
| | - M. Jamal Deen
- School of Biomedical Engineering, McMaster University, Hamilton, ON L8S 4L8, Canada;
- Department of Electrical and Computer Engineering, McMaster University, Hamilton, ON L8S 4L8, Canada;
- Correspondence: or ; Tel.: +1-905-525-9140 (ext. 27137)
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