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Li A, Zhang X, Zhou X, Fang L, Hu J, Li B, Zhang B, Xie Q, Li F, Xiao P. Timing offset calibration for TOF PET using stationary line source scans at multiple positions. Phys Med Biol 2024; 69:175018. [PMID: 39137804 DOI: 10.1088/1361-6560/ad6edb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Accepted: 08/13/2024] [Indexed: 08/15/2024]
Abstract
Background. Accurate timing offset calibration is crucial for time-of-flight (TOF) positron emission tomography (PET) to mitigate image artifacts and improve quantitative accuracy. However, existing methods are often time-consuming, complex, or costly.Objective. This paper presents a method for TOF PET timing offset calibration that eliminates the need for costly equipment, phantoms, short-half-life sources, and precise source positioning.Approach. We estimate channel timing offsets using stationary scans of a68Ge line source, typically used for routine quality control, at a minimum of three non-coplanar positions, with each position scanned for two minutes. The line source positions are accurately determined by applying a simple algorithm to their reconstructed images, allowing precise calculation of arrival time differences. Channel timing offsets are estimated by solving a least squares problem. This method is assessed through analyses of phantoms and patient images using a RAYSOLUTION DigitMI 930 scanner.Main results. The estimated timing offsets ranged from -500 ps to 500 ps across all channels. Calibration with a minimum of three scanned positions was sufficient to correct these offsets, achieving less than a 1% discrepancy across various metrics of the image quality (IQ) phantom compared to 12 positions. This calibration significantly reduced edge artifacts in TOF reconstruction of both phantoms and patients. Furthermore, the IQ phantom displayed a 14% increase in average contrast recovery, a 61% reduction in average background variability across all spheres, and a 90% reduction in average residual error. Consistent with the phantom results, patient data revealed enhancements in maximum standardized uptake values (SUVmax) from 14% to 55% for lesions measuring 6 mm to 14 mm. The calibration also improved lesion-to-background contrast and eliminated artifacts caused by the spillover effect of the kidneys and bladder.Significance. The proposed method is fast, user-friendly, and cost-effective, effectively improving lesion detection and diagnostic accuracy.
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Affiliation(s)
- Ang Li
- Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Xuan Zhang
- School of Artificial Intelligence and Automation, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Xiaoyun Zhou
- Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Lei Fang
- Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Junpeng Hu
- Department of Electronic Engineering and Information Science, University of Science and Technology of China, Hefei, People's Republic of China
| | - Bingxuan Li
- Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, People's Republic of China
| | - Bo Zhang
- Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Qingguo Xie
- Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People's Republic of China
- Department of Electronic Engineering and Information Science, University of Science and Technology of China, Hefei, People's Republic of China
- Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, People's Republic of China
| | - Fei Li
- Department of Nuclear Medicine, Second Affiliated Hospital of Anhui Medical University, Hefei, People's Republic of China
| | - Peng Xiao
- Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan, People's Republic of China
- Department of Electronic Engineering and Information Science, University of Science and Technology of China, Hefei, People's Republic of China
- Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, People's Republic of China
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Naunheim S, Kuhl Y, Solf T, Schug D, Schulz V, Mueller F. Analysis of a convex time skew calibration for light sharing-based PET detectors. Phys Med Biol 2023; 68. [PMID: 36595338 DOI: 10.1088/1361-6560/aca872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 12/01/2022] [Indexed: 12/05/2022]
Abstract
Objective.Positron emission tomography (PET) detectors providing attractive coincidence time resolutions (CTRs) offer time-of-flight information, resulting in an improved signal-to-noise ratio of the PET image. In applications with photosensor arrays that employ timestampers for individual channels, timestamps typically are not time synchronized, introducing time skews due to different signal pathways. The scintillator topology and transportation of the scintillation light might provoke further skews. If not accounted for these effects, the achievable CTR deteriorates. We studied a convex timing calibration based on a matrix equation. In this work, we extended the calibration concept to arbitrary structures targeting different aspects of the time skews and focusing on optimizing the CTR performance for detector characterization. The radiation source distribution, the stability of the estimations, and the energy dependence of calibration data are subject to the analysis.Approach.A coincidence setup, equipped with a semi-monolithic detector comprising 8 LYSO slabs, each 3.9 mm × 31.9 mm × 19.0 mm, and a one-to-one coupled detector with 8 × 8 LYSO segments of 3.9 mm × 3.9 mm × 19.0 mm volume is used. Both scintillators utilize a dSiPM (DPC3200-22-44, Philips Digital Photon Counting) operated in first photon trigger. The calibration was also conducted with solely one-to-one coupled detectors and extrapolated for a slab-only setup.Main results.All analyzed hyperparameters show a strong influence on the calibration. Using multiple radiation positions improved the skew estimation. The statistical significance of the calibration dataset and the utilized energy window was of great importance. Compared to a one-to-one coupled detector pair achieving CTRs of 224 ps the slab detector configuration reached CTRs down to 222 ps, demonstrating that slabs can compete with a clinically used segmented detector design.Significance.This is the first work that systematically studies the influence of hyperparameters on skew estimation and proposes an extension to arbitrary calibration structures (e.g. scintillator volumes) of a known calibration technique.
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Affiliation(s)
- Stephan Naunheim
- Department of Physics of Molecular Imaging Systems (PMI), Institute for Experimental Imaging, RWTH Aachen University, Germany
| | - Yannick Kuhl
- Department of Physics of Molecular Imaging Systems (PMI), Institute for Experimental Imaging, RWTH Aachen University, Germany
| | - Torsten Solf
- Philips Digital Photon Counting, Aachen, Germany
| | - David Schug
- Department of Physics of Molecular Imaging Systems (PMI), Institute for Experimental Imaging, RWTH Aachen University, Germany.,Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany
| | - Volkmar Schulz
- Department of Physics of Molecular Imaging Systems (PMI), Institute for Experimental Imaging, RWTH Aachen University, Germany.,Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany.,Fraunhofer Institute for Digital Medicine MEVIS, Aachen, Germany.,Physics Institute III B, RWTH Aachen University, Aachen, Germany
| | - Florian Mueller
- Department of Physics of Molecular Imaging Systems (PMI), Institute for Experimental Imaging, RWTH Aachen University, Germany
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Chen H, Liu H. Deep learning based timing calibration for PET. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:3185-3188. [PMID: 34891918 DOI: 10.1109/embc46164.2021.9630519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Neural network has been found an increasingly wide utilization in all fields. Owing to the fact that the traditional optimized algorithm, Iterative Shrinkage-Thresholding Algorithm (ISTA) or Alternating Direction Method of Multi-pliers (ADMM), could be presented by a form of network, and it could overcome some shortcomings of traditional algorithms, which inspired us to introduce the structured deep network into PET timing calibration. In this paper, by reformulating an ADMM algorithm to a deep network, we introduce a ADMM-Net framework for calibration, which combines the advantage of compatibility of consistency condition method. To verify the performance, several experiments of Monte Carlo simulation in GATE are performed.
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Loignon-Houle F, Toussaint M, Sun Lee M, Cates JW, Lecomte R. Experimental validation of a coincidence time resolution metric including depth-of-interaction bias for TOF-PET. ACTA ACUST UNITED AC 2020; 65:245004. [DOI: 10.1088/1361-6560/aba7d0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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