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Ko GB, Lee JS. Dual threshold input receiver FPGA-only signal digitization method for time-of-flight positron emission tomography. Biomed Eng Lett 2024; 14:847-858. [PMID: 38946816 PMCID: PMC11208371 DOI: 10.1007/s13534-024-00380-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2024] [Accepted: 04/07/2024] [Indexed: 07/02/2024] Open
Abstract
As silicon photomultiplier (SiPM)-based time-of-flight (TOF) positron emission tomography (PET) becomes popular, the need for sophisticated PET data acquisition (DAQ) systems is increasing. One promising solution to this challenge is the adoption of a field-programmable gate array (FPGA)-only signal digitization method. In this paper, we propose a new approach to efficiently implement an FPGA-only digitizer. We configured the input/output (IO) port of the FPGA to function as a dual-threshold voltage comparator through the use of simple passive circuitry and heterogeneous IO standards. This configuration overcomes the limitations of existing methods by allowing different threshold voltages for adjacent IO pins, effectively reducing routing complexity and lowering manufacturing costs. An FPGA-only digitizer was implemented by integrating the dual-threshold voltage comparator and FPGA-based time-to-digital converter. By combining the dual-threshold time-over-threshold (TOT) method and curve fitting, precise energy information could be obtained. The performance of the FPGA-only digitizer was assessed using a detector setup comprising a 3 × 3 × 20 mm3 LYSO scintillation crystal and a single pixel SiPM. Using the configured evaluation setup, an energy resolution of 12.5% and a time resolution of 146 ± 9 ps were achieved for a 20 mm scintillation crystal. The dual-threshold TOT implemented using the proposed method showed consistent linearity across an energy range of 100 keV to 600 keV. The proposed method is well-suited for the development of cost-effective DAQ systems in highly integrated TOF PET systems.
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Affiliation(s)
- Guen Bae Ko
- Brightonix Imaging Inc., Seoul, 04782 South Korea
- Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, 03080 South Korea
| | - Jae Sung Lee
- Brightonix Imaging Inc., Seoul, 04782 South Korea
- Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, 03080 South Korea
- Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, 03080 South Korea
- Interdisciplinary Program in Bioengineering, College of Engineering, Seoul National University, Seoul, 03080 South Korea
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Yoshida E, Yamaya T. PET detectors with depth-of-interaction and time-of-flight capabilities. Radiol Phys Technol 2024:10.1007/s12194-024-00821-x. [PMID: 38888821 DOI: 10.1007/s12194-024-00821-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: 05/07/2024] [Revised: 06/09/2024] [Accepted: 06/09/2024] [Indexed: 06/20/2024]
Abstract
In positron emission tomography (PET), measurements of depth-of-interaction (DOI) information and time-of-flight (TOF) information are important. DOI information reduces the parallax error, and TOF information reduces noise by measuring the arrival time difference of the annihilation photons. Historically, these have been studied independently, and there has been less implementation of both DOI and TOF capabilities because previous DOI detectors did not have good TOF resolution. However, recent improvements in PET detector performance have resulted in commercial PET scanners achieving a coincidence resolving time of around 200 ps, which result in an effect even for small objects. This means that TOF information can now be utilized even for a brain PET scanner, which also requires DOI information. Therefore, various methods have been proposed to obtain better DOI and TOF information. In addition, the cost of PET detectors is also an important factor to consider, since several hundred detectors are used per PET scanner. In this paper, we review the latest DOI-TOF detectors including the history of detector development. When put into practical use, these DOI-TOF detectors are expected to contribute to the improvement of imaging performance in brain PET scanners.
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Affiliation(s)
- Eiji Yoshida
- National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
| | - Taiga Yamaya
- National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
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3
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Zeng X, LaBella A, Wang Z, Li Y, Tan W, Goldan AH. Depth-encoding using optical photon TOF in a prism-PET detector with tapered crystals. Med Phys 2024; 51:4044-4055. [PMID: 38682574 DOI: 10.1002/mp.17095] [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: 01/05/2024] [Revised: 03/11/2024] [Accepted: 04/10/2024] [Indexed: 05/01/2024] Open
Abstract
BACKGROUND High-resolution brain positron emission tomography (PET) scanner is emerging as a significant and transformative non-invasive neuroimaging tool to advance neuroscience research as well as improve diagnosis and treatment in neurology and psychiatry. Time-of-flight (TOF) and depth-of-interaction (DOI) information provide markedly higher PET imaging performance by increasing image signal-to-noise ratio and mitigating spatial resolution degradation due to parallax error, respectively. PET detector modules that utilize light sharing can inherently carry DOI information from the multiple timestamps that are generated per gamma event. The difference between two timestamps that are triggered by scintillation photons traveling in opposite directions signifies the event's depth-dependent optical photon TOF (oTOF). However, light leak at the crystal-readout interface substantially degrades the resolution of this oTOF-based depth encoding. PURPOSE We demonstrate the feasibility of oTOF-based depth encoding by mitigating light leak in single-ended-readout Prism-PET detector modules using tapered crystals. Minimizing light leak also improved both energy-based DOI and coincidence timing resolutions. METHODS The tapered Prism-PET module consists of a 16 × $\times$ 16 array of 1.5 × $\times$ 1.5 × $\times$ 20 mm 3 ${\rm {mm}}^3$ lutetium yttrium oxyorthosillicate (LYSO) crystals, which are tapered down to 1.2 × $\times$ 1.2 mm 2 ${\rm {mm}}^2$ at the crystal-readout interface. The LYSO array couples 4-to-1 to an 8 × $\times$ 8 array of 3 × $\times$ 3 mm 2 ${\rm {mm}}^2$ silicon photomultiplier (SiPM) pixels on the tapered end and to a segmented prismatoid light guide array on the opposite end. Performance of tapered and non-tapered Prism-PET detectors was experimentally characterized and evaluated by measuring flood histogram, energy resolution, energy-, and oTOF-based DOI resolutions, and coincidence timing resolution. Sensitivities of scanners using different Prism-PET detector designs were simulated using Geant4 application for tomographic emission (GATE). RESULTS For the tapered (non-tapered) Prism-PET module, the measured full width at half maximum (FWHM) energy, timing, energy-based DOI, and oTOF-based DOI resolutions were 8.88 (11.18)%, 243 (286) ps, 2.35 (3.18) mm, and 5.42 (13.87) mm, respectively. The scanner sensitivities using non-tapered and tapered crystals, and 10 rings of detector modules, were simulated to be 30.9 and 29.5 kcps/MBq, respectively. CONCLUSIONS The tapered Prism-PET module with minimized light leak enabled the first experimental report of oTOF-based depth encoding at the detector module level. It also enabled the utilization of thinner (i.e., 0.1 mm) inter-crystal spacing with barium sulfate as the reflector while also improving energy-based DOI and timing resolutions.
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Affiliation(s)
- Xinjie Zeng
- Department of Radiology, Weill Cornell Medical College, Cornell University, New York, New York, USA
- Department of Electrical and Computer Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, New York, USA
| | - Andy LaBella
- Department of Radiology, Renaissance School of Medicine, Stony Brook University, Stony Brook, New York, USA
| | - Zipai Wang
- Department of Radiology, Weill Cornell Medical College, Cornell University, New York, New York, USA
- Department of Biomedical Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, New York, USA
| | - Yixin Li
- Department of Radiology, Weill Cornell Medical College, Cornell University, New York, New York, USA
- Department of Electrical and Computer Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, New York, USA
| | - Wanbin Tan
- Department of Radiology, Weill Cornell Medical College, Cornell University, New York, New York, USA
- Department of Biomedical Engineering, College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, New York, USA
| | - Amir H Goldan
- Department of Radiology, Weill Cornell Medical College, Cornell University, New York, New York, USA
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Higuchi T, Chen X, Werner RA. Navigating new horizons: Prospects of NET-targeted radiopharmaceuticals in precision medicine. Theranostics 2024; 14:3178-3192. [PMID: 38855189 PMCID: PMC11155404 DOI: 10.7150/thno.96743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Accepted: 04/23/2024] [Indexed: 06/11/2024] Open
Abstract
In the evolving landscape of precision medicine, NET-targeted radiopharmaceuticals are emerging as pivotal tools for the diagnosis and treatment of a range of conditions, from heart failure and neurodegenerative disorders to neuroendocrine cancers. This review evaluates the advancements offered by 18F-labeled PET tracers and 211At alpha-particle therapy, juxtaposed with current 123I-MIBG SPECT and 131I-MIBG therapies. The enhanced spatial resolution and capability for quantitative analysis render 18F-labeled PET tracers potential candidates for improved detection and management of diseases. Alpha-particle therapy with 211At may offer increased specificity and tumoricidal efficacy, pointing towards a shift in therapeutic protocols. While preliminary data is promising, these innovative approaches require thorough validation against current modalities. Ongoing clinical trials are pivotal to confirm the expected clinical benefits and to address safety concerns. This review underscores the need for rigorous research to verify the clinical utility of NET-targeted radiopharmaceuticals, which may redefine precision medicine paradigms and significantly impact patient care.
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Affiliation(s)
- Takahiro Higuchi
- Department of Nuclear Medicine and Comprehensive Heart Failure Center, University Hospital of Würzburg, Würzburg, Germany
- Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Xinyu Chen
- Nuclear Medicine, Faculty of Medicine, University of Augsburg, Augsburg, Germany
| | - Rudolf A Werner
- DZHK (German Centre for Cardiovascular Research), Partner Site Frankfurt Rhine-Main, Frankfurt, Germany
- Goethe University Frankfurt, Department of Nuclear Medicine, Clinic for Radiology and Nuclear Medicine, Frankfurt, Germany
- German Cancer Consortium (DKTK), Partner Site Frankfurt/Mainz and German Cancer Research Center (DKFZ), Heidelberg, Germany
- The Russell H Morgan Department of Radiology and Radiological Sciences, Division of Nuclear Medicine and Molecular Imaging, Johns Hopkins School of Medicine, Baltimore, MD, United States
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Hahn A, Reed MB, Vraka C, Godbersen GM, Klug S, Komorowski A, Falb P, Nics L, Traub-Weidinger T, Hacker M, Lanzenberger R. High-temporal resolution functional PET/MRI reveals coupling between human metabolic and hemodynamic brain response. Eur J Nucl Med Mol Imaging 2024; 51:1310-1322. [PMID: 38052927 DOI: 10.1007/s00259-023-06542-4] [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: 08/25/2023] [Accepted: 11/22/2023] [Indexed: 12/07/2023]
Abstract
PURPOSE Positron emission tomography (PET) provides precise molecular information on physiological processes, but its low temporal resolution is a major obstacle. Consequently, we characterized the metabolic response of the human brain to working memory performance using an optimized functional PET (fPET) framework at a temporal resolution of 3 s. METHODS Thirty-five healthy volunteers underwent fPET with [18F]FDG bolus plus constant infusion, 19 of those at a hybrid PET/MRI scanner. During the scan, an n-back working memory paradigm was completed. fPET data were reconstructed to 3 s temporal resolution and processed with a novel sliding window filter to increase signal to noise ratio. BOLD fMRI signals were acquired at 2 s. RESULTS Consistent with simulated kinetic modeling, we observed a constant increase in the [18F]FDG signal during task execution, followed by a rapid return to baseline after stimulation ceased. These task-specific changes were robustly observed in brain regions involved in working memory processing. The simultaneous acquisition of BOLD fMRI revealed that the temporal coupling between hemodynamic and metabolic signals in the primary motor cortex was related to individual behavioral performance during working memory. Furthermore, task-induced BOLD deactivations in the posteromedial default mode network were accompanied by distinct temporal patterns in glucose metabolism, which were dependent on the metabolic demands of the corresponding task-positive networks. CONCLUSIONS In sum, the proposed approach enables the advancement from parallel to truly synchronized investigation of metabolic and hemodynamic responses during cognitive processing. This allows to capture unique information in the temporal domain, which is not accessible to conventional PET imaging.
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Affiliation(s)
- Andreas Hahn
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria.
- Comprehensive Center for Clinical Neurosciences and Mental Health (C3NMH), Medical University of Vienna, Vienna, Austria.
| | - Murray B Reed
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health (C3NMH), Medical University of Vienna, Vienna, Austria
| | - Chrysoula Vraka
- Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria
| | - Godber M Godbersen
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health (C3NMH), Medical University of Vienna, Vienna, Austria
| | - Sebastian Klug
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health (C3NMH), Medical University of Vienna, Vienna, Austria
| | - Arkadiusz Komorowski
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health (C3NMH), Medical University of Vienna, Vienna, Austria
| | - Pia Falb
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health (C3NMH), Medical University of Vienna, Vienna, Austria
| | - Lukas Nics
- Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria
| | - Tatjana Traub-Weidinger
- Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria
| | - Marcus Hacker
- Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria
| | - Rupert Lanzenberger
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria.
- Comprehensive Center for Clinical Neurosciences and Mental Health (C3NMH), Medical University of Vienna, Vienna, Austria.
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Dedja M, Mehranian A, Bradley KM, Walker MD, Fielding PA, Wollenweber SD, Johnsen R, McGowan DR. Sequential deep learning image enhancement models improve diagnostic confidence, lesion detectability, and image reconstruction time in PET. EJNMMI Phys 2024; 11:28. [PMID: 38488923 PMCID: PMC10942956 DOI: 10.1186/s40658-024-00632-4] [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: 10/22/2023] [Accepted: 03/07/2024] [Indexed: 03/17/2024] Open
Abstract
BACKGROUND Investigate the potential benefits of sequential deployment of two deep learning (DL) algorithms namely DL-Enhancement (DLE) and DL-based time-of-flight (ToF) (DLT). DLE aims to enhance the rapidly reconstructed ordered-subset-expectation-maximisation algorithm (OSEM) images towards block-sequential-regularised-expectation-maximisation (BSREM) images, whereas DLT aims to improve the quality of BSREM images reconstructed without ToF. As the algorithms differ in their purpose, sequential application may allow benefits from each to be combined. 20 FDG PET-CT scans were performed on a Discovery 710 (D710) and 20 on Discovery MI (DMI; both GE HealthCare). PET data was reconstructed using five combinations of algorithms:1. ToF-BSREM, 2. ToF-OSEM + DLE, 3. OSEM + DLE + DLT, 4. ToF-OSEM + DLE + DLT, 5. ToF-BSREM + DLT. To assess image noise, 30 mm-diameter spherical VOIs were drawn in both lung and liver to measure standard deviation of voxels within the volume. In a blind clinical reading, two experienced readers rated the images on a five-point Likert scale based on lesion detectability, diagnostic confidence, and image quality. RESULTS Applying DLE + DLT reduced noise whilst improving lesion detectability, diagnostic confidence, and image reconstruction time. ToF-OSEM + DLE + DLT reconstructions demonstrated an increase in lesion SUVmax of 28 ± 14% (average ± standard deviation) and 11 ± 5% for data acquired on the D710 and DMI, respectively. The same reconstruction scored highest in clinical readings for both lesion detectability and diagnostic confidence for D710. CONCLUSIONS The combination of DLE and DLT increased diagnostic confidence and lesion detectability compared to ToF-BSREM images. As DLE + DLT used input OSEM images, and because DL inferencing was fast, there was a significant decrease in overall reconstruction time. This could have applications to total body PET.
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Affiliation(s)
| | | | | | | | | | | | | | - Daniel R McGowan
- Oxford University Hospitals, Oxford, UK.
- University of Oxford, Oxford, UK.
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Gonzalez-Montoro A, Levin CS. PET System Technology: Theoretical Aspects and Experimental Methodology. Methods Mol Biol 2024; 2729:343-369. [PMID: 38006506 DOI: 10.1007/978-1-0716-3499-8_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2023]
Abstract
Positron emission tomography (PET) imaging provides unique information of the cellular and molecular pathways of disease occurring within the human body, using measurements made from outside the body, which has shown utility in a variety of studies from basic research to clinical applications. This chapter describes some of the most relevant PET system parameters that impact its imaging performance such as 3D spatial, energy, and coincidence timing resolutions and the methodology typically used to evaluate those parameters. In addition, the physical principles underlying PET imaging, PET photon detector technology, and coincidence detection are also described. As a closing remark, the future perspectives of PET imaging and its simultaneous use with anatomical imaging techniques (e.g., computed tomography [CT] and magnetic resonance imaging [MRI]) are outlined.
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Affiliation(s)
| | - Craig S Levin
- Department of Radiology, Stanford University, Stanford, CA, USA.
- Departments of Radiology, Bioengineering, Physics, and Electrical Engineering, Stanford University, Stanford, CA, USA.
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Singh MK. A review of digital PET-CT technology: Comparing performance parameters in SiPM integrated digital PET-CT systems. Radiography (Lond) 2024; 30:13-20. [PMID: 37864986 DOI: 10.1016/j.radi.2023.10.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 09/29/2023] [Accepted: 10/03/2023] [Indexed: 10/23/2023]
Abstract
OBJECTIVE The objective of this study was to perform a narrative review of digital Positron emission tomography-computed tomography (PET-CT) scanners, focussing on the current development in the technology of optimized crystal size and design, the time of flight (ToF) resolution, sensitivity, and axial field of view (AFOV). KEY FINDINGS It was observed that significant developments were carried out on the optimization of scintillation crystal size which results in the improvement of spatial resolution. such developments include the upgrade in the AFOV after the integration of SiPM technology, which results in dynamic parametric imaging acquisition in PET and sensitivity boost. The improvement in ToF resolution and the better ToF resolution values, which result in a boost in adequate sensitivity and signal-to-noise ratio (SNR). Other upgrades include the use of the smallest crystal size of 2.76 × 2.76 mm, and the use of the lowest ToF resolution of 214 ps. The use of the largest AFOV of 194 cm with the highest observed NEMA sensitivity of 225 cps/kBq for the total body PET-CT system. CONCLUSION Digital PET-CT systems offer various advantages such as a reduction in radiation dose from injected radiopharmaceuticals doses and the overall PET acquisition time with an improved diagnostic certainty. This is because of the better performance of the SiPM detector. Digital PET-CT also has added benefits of the dynamic acquisition and Patlak modeling capabilities into routine clinical practice with the advancement in higher AFOV PET systems. IMPLICATION This will help the users choose the best system during the evaluation of the PET-CT for purchase in clinical and research applications. This review will further help in teaching the latest technology and developments in PET-CT systems.
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Affiliation(s)
- M K Singh
- AECC University College, Parkwood Road, Bournemouth, UK.
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Lee JS, Lee MS. Advancements in Positron Emission Tomography Detectors: From Silicon Photomultiplier Technology to Artificial Intelligence Applications. PET Clin 2024; 19:1-24. [PMID: 37802675 DOI: 10.1016/j.cpet.2023.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/08/2023]
Abstract
This review article focuses on PET detector technology, which is the most crucial factor in determining PET image quality. The article highlights the desired properties of PET detectors, including high detection efficiency, spatial resolution, energy resolution, and timing resolution. Recent advancements in PET detectors to improve these properties are also discussed, including the use of silicon photomultiplier technology, advancements in depth-of-interaction and time-of-flight PET detectors, and the use of artificial intelligence for detector development. The article provides an overview of PET detector technology and its recent advancements, which can significantly enhance PET image quality.
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Affiliation(s)
- Jae Sung Lee
- Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul 03080, South Korea; Brightonix Imaging Inc., Seoul 04782, South Korea
| | - Min Sun Lee
- Environmental Radioactivity Assessment Team, Nuclear Emergency & Environmental Protection Division, Korea Atomic Energy Research Institute, Daejeon 34057, South Korea.
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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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Renaud JM, Poitrasson-Rivière A, Moody JB, Hagio T, Ficaro EP, Murthy VL. Improved diagnostic accuracy for coronary artery disease detection with quantitative 3D 82Rb PET myocardial perfusion imaging. Eur J Nucl Med Mol Imaging 2023; 51:147-158. [PMID: 37721579 DOI: 10.1007/s00259-023-06414-x] [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: 05/31/2023] [Accepted: 08/22/2023] [Indexed: 09/19/2023]
Abstract
PURPOSE To establish requirements for normal databases for quantitative rubidium-82 (82Rb) PET MPI analysis with contemporary 3D PET/CT technology and reconstruction methods for maximizing diagnostic accuracy of total perfusion deficit (TPD), a combined metric of defect extent and severity, versus invasive coronary angiography. METHODS In total, 1571 patients with 82Rb PET/CT MPI on a 3D scanner and stress static images reconstructed with and without time-of-flight (TOF) modeling were identified. An additional eighty low pre-test probability of disease (PTP) patients reported as normal were used to form separate sex-stratified and sex-independent iterative and TOF normal databases. 3D normal databases were applied to matched patient reconstructions to quantify TPD. Per-patient and per-vessel performance of 3D versus 2D PET normal databases was assessed with receiver operator characteristic curve analysis. Diagnostic accuracy was evaluated at optimal thresholds established from PTP patients. Results were compared against logistic regression modeling of TPD adjusted for clinical variables, and standard clinical interpretation. RESULTS TPD diagnostic accuracy was significantly higher using 3D PET normal databases (per-patient: 80.1% for 3D databases, versus 74.9% and 77.7% for 2D database applied to iterative and TOF images respectively, p < 0.05). Differences in male and female normal distributions for 3D attenuation-corrected reconstructions were not clinically meaningful; therefore, sex-independent databases were used. Logistic regression modeling including TPD demonstrated improved performance over clinical reads. CONCLUSIONS Normal databases tailored to 3D PET images provide significantly improved diagnostic accuracy for PET MPI evaluation with automated quantitative TPD. Clinical application of these techniques should be considered to support accurate image interpretation.
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Affiliation(s)
- Jennifer M Renaud
- INVIA Medical Imaging Solutions, 3025 Boardwalk Dr., Suite 200, Ann Arbor, MI, 48108, USA.
| | | | - Jonathan B Moody
- INVIA Medical Imaging Solutions, 3025 Boardwalk Dr., Suite 200, Ann Arbor, MI, 48108, USA
| | - Tomoe Hagio
- INVIA Medical Imaging Solutions, 3025 Boardwalk Dr., Suite 200, Ann Arbor, MI, 48108, USA
| | - Edward P Ficaro
- INVIA Medical Imaging Solutions, 3025 Boardwalk Dr., Suite 200, Ann Arbor, MI, 48108, USA
| | - Venkatesh L Murthy
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
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Chen X, Gallagher F, Sellmyer MA, Ordonez AA, Kjaer A, Ohliger M, Wilson DM, Jain SK. Visualizing Bacterial Infections With Novel Targeted Molecular Imaging Approaches. J Infect Dis 2023; 228:S249-S258. [PMID: 37788506 PMCID: PMC10547462 DOI: 10.1093/infdis/jiad078] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/05/2023] Open
Abstract
Although nearly a century has elapsed since the discovery of penicillin, bacterial infections remain a major global threat. Global antibiotic use resulted in an astounding 42 billion doses of antibiotics administered in 2015 with 128 billion annual doses expected by 2030. This overuse of antibiotics has led to the selection of multidrug-resistant "super-bugs," resulting in increasing numbers of patients being susceptible to life-threatening infections with few available therapeutic options. New clinical tools are therefore urgently needed to identify bacterial infections and monitor response to antibiotics, thereby limiting overuse of antibiotics and improving overall health. Next-generation molecular imaging affords unique opportunities to target and identify bacterial infections, enabling spatial characterization as well as noninvasive, temporal monitoring of the natural course of the disease and response to therapy. These emerging noninvasive imaging approaches could overcome several limitations of current tools in infectious disease, such as the need for biological samples for testing with their associated sampling bias. Imaging of living bacteria can also reveal basic biological insights about their behavior in vivo.
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Affiliation(s)
- Xueyi Chen
- Center for Infection and Inflammation Imaging Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Center for Tuberculosis Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Ferdia Gallagher
- Department of Radiology, University of Cambridge, Cambridge, United Kingdom
| | - Mark A Sellmyer
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Alvaro A Ordonez
- Center for Infection and Inflammation Imaging Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Center for Tuberculosis Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Andreas Kjaer
- Department of Clinical Physiology and Nuclear Medicine and Cluster for Molecular Imaging, Copenhagen University Hospital-Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Michael Ohliger
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, USA
| | - David M Wilson
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, USA
| | - Sanjay K Jain
- Center for Infection and Inflammation Imaging Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Center for Tuberculosis Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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13
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Gu F, Wu Q. Quantitation of dynamic total-body PET imaging: recent developments and future perspectives. Eur J Nucl Med Mol Imaging 2023; 50:3538-3557. [PMID: 37460750 PMCID: PMC10547641 DOI: 10.1007/s00259-023-06299-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 06/05/2023] [Indexed: 10/04/2023]
Abstract
BACKGROUND Positron emission tomography (PET) scanning is an important diagnostic imaging technique used in disease diagnosis, therapy planning, treatment monitoring, and medical research. The standardized uptake value (SUV) obtained at a single time frame has been widely employed in clinical practice. Well beyond this simple static measure, more detailed metabolic information can be recovered from dynamic PET scans, followed by the recovery of arterial input function and application of appropriate tracer kinetic models. Many efforts have been devoted to the development of quantitative techniques over the last couple of decades. CHALLENGES The advent of new-generation total-body PET scanners characterized by ultra-high sensitivity and long axial field of view, i.e., uEXPLORER (United Imaging Healthcare), PennPET Explorer (University of Pennsylvania), and Biograph Vision Quadra (Siemens Healthineers), further stimulates valuable inspiration to derive kinetics for multiple organs simultaneously. But some emerging issues also need to be addressed, e.g., the large-scale data size and organ-specific physiology. The direct implementation of classical methods for total-body PET imaging without proper validation may lead to less accurate results. CONCLUSIONS In this contribution, the published dynamic total-body PET datasets are outlined, and several challenges/opportunities for quantitation of such types of studies are presented. An overview of the basic equation, calculation of input function (based on blood sampling, image, population or mathematical model), and kinetic analysis encompassing parametric (compartmental model, graphical plot and spectral analysis) and non-parametric (B-spline and piece-wise basis elements) approaches is provided. The discussion mainly focuses on the feasibilities, recent developments, and future perspectives of these methodologies for a diverse-tissue environment.
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Affiliation(s)
- Fengyun Gu
- School of Mathematics and Physics, North China Electric Power University, 102206, Beijing, China.
- School of Mathematical Sciences, University College Cork, T12XF62, Cork, Ireland.
| | - Qi Wu
- School of Mathematical Sciences, University College Cork, T12XF62, Cork, Ireland
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Lee D, Cherry SR, Kwon SI. Colored reflectors to improve coincidence timing resolution of BGO-based time-of-flight PET detectors. Phys Med Biol 2023; 68:10.1088/1361-6560/acf027. [PMID: 37579768 PMCID: PMC10722960 DOI: 10.1088/1361-6560/acf027] [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: 02/03/2023] [Accepted: 08/14/2023] [Indexed: 08/16/2023]
Abstract
Time-of-flight (TOF) positron emission tomography (PET) detectors improve the signal-to-noise ratio of PET images by limiting the position of the generation of two 511 keV gamma-rays in space using the arrival time difference between the two photons. Unfortunately, bismuth germanate (BGO), widely used in conventional PET detectors, was limited as a TOF PET scintillator due to the relatively slow decay time of the scintillation photons. However, prompt Cerenkov light in BGO has been identified in addition to scintillation photons. Using Cerenkov photons for timing has significantly improved the coincidence timing resolution (CTR) of BGO. Based on this, further research on improving the CTR for a BGO-based TOF PET system is being actively conducted. Wrapping materials for BGO pixels have primarily employed white reflectors to most efficiently collect scintillation light. White reflectors have customarily been used as reflectors for BGO pixels even after Cerenkov light began to be utilized for timing calculations in pixel-level experiments. However, when the arrival-time differences of the two 511 keV annihilations photons were measured with pure Cerenkov radiators, painting the lateral sides of the radiators black can improve CTR by suppressing the reflection of Cerenkov photons. The use of BGO for TOF PET detectors requires simultaneously minimizing scintillation loss for good energy information and suppressing reflected Cerenkov photons for better timing performance. Thus, reflectors for BGO pixels should be optimized for better timing and energy performance. In this study, colored polytetrafluoroethylene (PTFE) tapes with discontinuous reflectance values at specific wavelengths were applied as a BGO reflector. We hypothesized that CTR could be enhanced by selectively suppressing reflected Cerenkov photons with an optimum colored reflector on the BGO pixel while minimizing scintillation photon loss. CTRs were investigated utilizing white and three colors (yellow, red, and green) PTFE tapes as a reflector. In addition, black-painted PTFE tape and enhanced specular reflector film were investigated as reference reflector materials. When 3 × 3 × 20 mm3BGO pixels were wrapped with the yellow PTFE reflector, the CTR was significantly improved to 365 ± 5 ps from 403 ± 14 ps measured with the conventional white PTFE reflector. Adequate energy information was still obtained with only 4.1% degradation in light collection compared to the white reflector. Colored reflectors show the possibility to further improve CTR for BGO pixels with optimum reflectance design.
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Affiliation(s)
- Daehee Lee
- Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, United States of America
| | - Simon R Cherry
- Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, United States of America
| | - Sun Il Kwon
- Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, United States of America
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Loignon-Houle F, Toussaint M, Bertrand É, Lemyre FC, Lecomte R. Timing Estimation and Limits in TOF-PET Detectors Producing Prompt Photons. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2023; 7:692-703. [PMID: 38156329 PMCID: PMC10751813 DOI: 10.1109/trpms.2023.3279455] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2023]
Abstract
The production of prompt photons providing high photon time densities is a promising avenue to reach ultrahigh coincidence time resolution (CTR) in time-of-flight PET. Detectors producing prompt photons are receiving high interest experimentally, ignited by past exploratory theoretical studies that have anchored some guiding principles. Here, we aim to consolidate and extend the foundations for the analytical modeling of prompt generating detectors. We extend the current models to a larger range of prompt emission kinetics where more stringent requirements on the prompt photon yield rapidly emerge as a limiting factor. Lower bound and estimator evaluations are investigated with different underlying models, notably by merging or keeping separate the prompt and scintillation photon populations. We further show the potential benefits of knowing the proportion of prompt photons within a detection set to improve the CTR by mitigating the detrimental effect of population (prompt vs scintillation) mixing. Taking into account the fluctuations on the average number of detected prompt photons in the model reveals a limited influence when prompt photons are accompanied by fast scintillation (e.g., LSO:Ce:Ca) but a more significant effect when accompanied by slower scintillation (e.g., BGO). Establishing performance characteristics and limitations of prompt generating detectors is paramount to gauging and targeting the best possible timing capabilities they can offer.
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Affiliation(s)
- Francis Loignon-Houle
- Sherbrooke Molecular Imaging Center of CRCHUS and with the Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada, currently with Instituto de Instrumentación para Imagen Molecular, Centro Mixto CSIC-Universitat Politècnica de València, 46022 Valencia, Spain
| | - Maxime Toussaint
- Sherbrooke Molecular Imaging Center of CRCHUS and with the Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Émilie Bertrand
- CRCHUS and with the Department of Mathematics, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Félix Camirand Lemyre
- CRCHUS and with the Department of Mathematics, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Roger Lecomte
- Sherbrooke Molecular Imaging Center of CRCHUS and with the Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada, and also with IR&T Inc., Sherbrooke, QC, Canada
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Weindel K, Nadig V, Herweg K, Schulz V, Gundacker S. A time-based double-sided readout concept of 100 mm LYSO:Ce,Ca fibres for future axial TOF-PET. EJNMMI Phys 2023; 10:43. [PMID: 37450099 PMCID: PMC10349027 DOI: 10.1186/s40658-023-00563-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 07/05/2023] [Indexed: 07/18/2023] Open
Abstract
BACKGROUND Positron emission tomography (PET) requires a high signal-to-noise ratio (SNR) to improve image quality, with time-of-flight (TOF) being an effective way to boost the SNR. However, the scanner sensitivity and resolution must be maintained. The use of axially aligned 100-mm LYSO:Ce,Ca scintillation crystals with double-sided readout has the potential of ground-breaking TOF and sensitivity, while reducing parallax errors through depth-of-interaction (DOI) estimation, and also allowing a reduction in the number of readout channels required, resulting in cost benefits. Due to orientation, these fibres may also facilitate the integration of TOF-PET with magnetic resonance imaging (MRI) in hybrid imaging systems. The challenge of achieving a good spatial resolution with such long axial fibres is directly related to the achievable TOF resolution. In this study, the timing performance and DOI resolution of emerging high-performance materials were investigated to assess the merits of this approach in organ-dedicated or total-body/large-scale PET imaging systems. METHODS LYSO:Ce,Ca scintillation fibres of 20 mm and 100 mm length were tested in various operating and readout configurations to determine the best achievable coincidence time resolution (CTR) and DOI resolution. The tests were performed using state-of-the-art high-frequency (HF) readout and commercially available silicon photomultipliers (SiPMs) from Broadcom Inc. RESULTS For the 100-mm fibre, an average CTR performance of [Formula: see text] ps FWHM and an average depth-of-interaction resolution within the fibre of [Formula: see text] mm FWHM could be obtained. The 20-mm fibre showed a sub-100 ps CTR of [Formula: see text] ps FWHM and a fibre resolution of [Formula: see text] mm FWHM in the double-sided readout configuration. CONCLUSION With modern SiPMs and crystals, a double-sided readout of long fibres can achieve excellent timing resolution and field-advancing TOF resolution, outperforming commercial PET systems. With 100-mm fibres, an electronic channel reduction of about a factor 2.5 is inherent, with larger reduction factors conceivable, which can lead to lower production costs. The spatial resolution was shown to be limited in the axial direction with 12 mm, but is defined to 3 mm in all other directions. Recent SiPM and scintillator developments are expected to improve on the time and spatial resolution to be investigated in future prototypes.
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Affiliation(s)
- Konstantin Weindel
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Vanessa Nadig
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany
| | - Katrin Herweg
- 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
- Physics Institute III B, RWTH Aachen University, Aachen, Germany
- Hyperion Hybrid Imaging Systems GmbH, 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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Sohn JH, Behr SC, Hernandez PM, Seo Y. Quantitative Assessment of Myocardial Ischemia With Positron Emission Tomography. J Thorac Imaging 2023; 38:247-259. [PMID: 33492046 PMCID: PMC8295411 DOI: 10.1097/rti.0000000000000579] [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] [Indexed: 11/26/2022]
Abstract
Recent advances in positron emission tomography (PET) technology and reconstruction techniques have now made quantitative assessment using cardiac PET readily available in most cardiac PET imaging centers. Multiple PET myocardial perfusion imaging (MPI) radiopharmaceuticals are available for quantitative examination of myocardial ischemia, with each having distinct convenience and accuracy profile. Important properties of these radiopharmaceuticals ( 15 O-water, 13 N-ammonia, 82 Rb, 11 C-acetate, and 18 F-flurpiridaz) including radionuclide half-life, mean positron range in tissue, and the relationship between kinetic parameters and myocardial blood flow (MBF) are presented. Absolute quantification of MBF requires PET MPI to be performed with protocols that allow the generation of dynamic multiframes of reconstructed data. Using a tissue compartment model, the rate constant that governs the rate of PET MPI radiopharmaceutical extraction from the blood plasma to myocardial tissue is calculated. Then, this rate constant ( K1 ) is converted to MBF using an established extraction formula for each radiopharmaceutical. As most of the modern PET scanners acquire the data only in list mode, techniques of processing the list-mode data into dynamic multiframes are also reviewed. Finally, the impact of modern PET technologies such as PET/CT, PET/MR, total-body PET, machine learning/deep learning on comprehensive and quantitative assessment of myocardial ischemia is briefly described in this review.
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Affiliation(s)
- Jae Ho Sohn
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA
| | - Spencer C. Behr
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA
| | | | - Youngho Seo
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA
- Department of Radiation Oncology, University of California, San Francisco, CA
- UC Berkeley-UCSF Graduate Program in Bioengineering, Berkeley and San Francisco, CA
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18
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Abi-Akl M, Dadgar M, Toufique Y, Bouhali O, Vandenberghe S. Monte Carlo simulation of the system performance of a long axial field-of-view PET based on monolithic LYSO detectors. EJNMMI Phys 2023; 10:37. [PMID: 37311926 DOI: 10.1186/s40658-023-00559-2] [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: 02/02/2023] [Accepted: 06/05/2023] [Indexed: 06/15/2023] Open
Abstract
BACKGROUND In light of the milestones achieved in PET design so far, further sensitivity improvements aim to optimise factors such as the dose, throughput, and detection of small lesions. While several longer axial field-of-view (aFOV) PET systems based on pixelated detectors have been installed, continuous monolithic scintillation detectors recently gained increased attention due to their depth of interaction capability and superior intrinsic resolution. As a result, the aim of this work is to present and evaluate the performance of two long aFOV, monolithic LYSO-based PET scanner designs. METHODS Geant4 Application for Tomographic Emission (GATE) v9.1 was used to perform the simulations. Scanner designs A and B have an aFOV of 36.2 cm (7 rings) and 72.6 cm (14 rings), respectively, with 40 detector modules per ring each and a bore diameter of 70 cm. Each module is a 50 × 50 × 16 mm3 monolithic LYSO crystal. Sensitivity, noise equivalent count rate (NECR), scatter fraction, spatial resolution, and image quality tests were performed based on NEMA NU-2018 standards. RESULTS The sensitivity of design A was calculated to be 29.2 kcps/MBq at the centre and 27 kcps/MBq at 10 cm radial offset; similarly, the sensitivity of design B was found to be 106.8 kcps/MBq and 98.3 kcps/MBq at 10 cm radial offset. NECR peaks were reached at activity concentrations beyond the range of activities used for clinical studies. In terms of spatial resolution, the values for the point sources were below 2 mm for the radial, tangential, and axial full width half maximum. The contrast recovery coefficient ranged from 53% for design B and 4:1 contrast ratio to 90% for design A and 8:1 ratio, with a reasonably low background variability. CONCLUSIONS Longer aFOV PET designs using monolithic LYSO have superior spatial resolution compared to current pixelated total-body PET (TB-PET) scanners. These systems combine high sensitivity with improved contrast recovery.
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Affiliation(s)
- Maya Abi-Akl
- Department of Electronics and Information Systems, Medical Image and Signal Processing, Ghent University, Ghent, Belgium.
- Division of Arts and Sciences, Texas A&M University at Qatar, Doha, Qatar.
| | - Meysam Dadgar
- Department of Electronics and Information Systems, Medical Image and Signal Processing, Ghent University, Ghent, Belgium
| | - Yassine Toufique
- Energy, Materials, Numerical Physics, Ecole Normal Supérieur (ENS), Abdelmalek Essaadi University, Tétouan, Morocco
| | - Othmane Bouhali
- Division of Arts and Sciences, Texas A&M University at Qatar, Doha, Qatar
| | - Stefaan Vandenberghe
- Department of Electronics and Information Systems, Medical Image and Signal Processing, Ghent University, Ghent, Belgium
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Xia M, Xie Z, Wang H, Jin T, Liu L, Kang J, Sang Z, Yan X, Wu B, Hu H, Tang J, Niu G. Sub-Nanosecond 2D Perovskite Scintillators by Dielectric Engineering. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2211769. [PMID: 36762587 DOI: 10.1002/adma.202211769] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 01/27/2023] [Indexed: 05/05/2023]
Abstract
Perovskite materials have demonstrated great potential for ultrafast scintillators with high light yield. However, the decay time of perovskite still cannot be further minimized into sub-nanosecond region, while sub-nanosecond scintillators are highly demanded in various radiation detection, including high speed X-ray imaging, time-of-flight based tomography or particle discrimination, and timing resolution measurement in synchrotron radiation facilities, etc. Here, a rational design strategy is showed to shorten the scintillation decay time, by maximizing the dielectric difference between organic amines and Pb-Br octahedral emitters in 2D organic-inorganic hybrid perovskites (OIHP). Benzimidazole (BM) with low dielectric constant inserted between [PbBr6 ]2- layers, resulting in a surprisingly large exciton binding energy (360.3 ± 4.8 meV) of 2D OIHP BM2 PbBr4 . The emitting decay time is shortened as 0.97 ns, which is smallest among all the perovskite materials. Moreover, the light yield is 3190 photons MeV-1 , which is greatly higher than conventional ultrafast scintillator BaF2 (1500 photons MeV-1 ). The rare combination of ultrafast decay time and considerable light yield renders BM2 PbBr4 excellent performance in γ-ray, neutron, α-particle detection, and the best theoretical coincidence time resolution of 65.1 ps, which is only half of the reference sample LYSO (141.3 ps).
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Affiliation(s)
- Mengling Xia
- Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Optical Valley Laboratory, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Zuoxiang Xie
- Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Optical Valley Laboratory, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Hanqi Wang
- Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Optical Valley Laboratory, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Tong Jin
- Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Optical Valley Laboratory, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Linyue Liu
- State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an, 710024, P. R. China
| | - Jun Kang
- Beijing Computational Science Research Center, Beijing, 100193, P. R. China
| | - Ziru Sang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, P. R. China
| | - Xianchang Yan
- State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, P. R. China
| | - Boning Wu
- State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, P. R. China
| | - Hao Hu
- Hubei Jiufengshan Laboratory, Wuhan, 430074, P. R. China
| | - Jiang Tang
- Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Optical Valley Laboratory, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Guangda Niu
- Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Optical Valley Laboratory, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
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20
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Modified signal-to-noise ratio in the liver using the background-to-lung activity ratio to assess image quality of whole-body 18F-fluorodeoxyglucose positron emission tomography. Radiol Phys Technol 2023; 16:94-101. [PMID: 36683121 DOI: 10.1007/s12194-023-00700-x] [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: 09/18/2022] [Revised: 01/14/2023] [Accepted: 01/16/2023] [Indexed: 01/24/2023]
Abstract
The signal-to-noise ratio in the liver (SNR liver) is commonly used to assess the quality of positron emission tomography (PET) images; however, it is weakly correlated with visual assessments. Conversely, the noise equivalent count (NEC) density showed a strong correlation with visual assessment but did not consider the effects of image reconstruction conditions. Therefore, we propose a new indicator, the modified SNR liver, and plan to verify its usefulness by comparing it with conventional indicators. We retrospectively analyzed 103 patients who underwent whole-body PET/computed tomography (CT). Approximately 60 min after the intravenous injection of 18F-fluorodeoxyglucose (FDG), the participants were scanned for 2 min/bed. The SNR liver and NEC density were calculated according to the Japanese guidelines for oncology FDG-PET/CT. The modified SNR live was calculated by multiplying the background-to-lung activity ratio by the SNR liver. Patients were classified into groups based on body mass index (BMI) and visual scores. Subsequently, the relationships between these physical indicators, BMI, and visual scores were evaluated. Although the relationship between the modified SNR liver and BMI was inferior to that of NEC density and BMI, the modified SNR liver distinguished the BMI groups more clearly than the conventional SNR liver. Additionally, the modified SNR liver distinguished low visual scores from high scores more accurately than the conventional SNR liver and NEC density. Whether the modified SNR liver is more suitable than the NEC density remains equivocal; however, the modified SNR liver may be superior to the conventional SNR liver for image-quality assessment.
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21
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Fragoso Costa P, Jentzen W, SÜßELBECK F, Fendler WP, Rischpler C, Herrmann K, Conti M, Kersting D, Weber M. Reduction of emission time for [68Ga]Ga-PSMA PET/CT using the digital biograph vision: a phantom study. THE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING : OFFICIAL PUBLICATION OF THE ITALIAN ASSOCIATION OF NUCLEAR MEDICINE (AIMN) [AND] THE INTERNATIONAL ASSOCIATION OF RADIOPHARMACOLOGY (IAR), [AND] SECTION OF THE SOCIETY OF... 2023; 67:57-68. [PMID: 34309334 DOI: 10.23736/s1824-4785.21.03300-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND The aim of this phantom study was to optimize the [68Ga]Ga-PSMA PET/CT examination in terms of scan time duration and image reconstruction parameters, in combination with PSF and TOF modelling, in a digital Biograph Vision PET/CT scanner. METHODS Three types of phantoms were used: 1) soft-tissue tumor phantom consisting of six spheres mounted in a torso phantom; 2) bone-lung tumor phantom; 3) resolution phantom. Phantom inserts were filled with activity concentrations (ACs) that were derived from clinical data. Phantom data were acquired in list-mode at one bed position. Images with emission data ranging from 30 to 210 s in 30-s increments were reconstructed from a reference image acquired with 3.5-min emission. Iterative image reconstruction (OSEM), point-spread-function (PSF) and time-of-flight (TOF) options were applied using different iterations, Gaussian filters, and voxel sizes. The criteria for image quality was lesion detectability and lesion quantification, evaluated as contrast-to-noise ratio (CNR) and maximum AC (peak AC), respectively. A threshold value of CNR above 6 and percentage maximum AC (peak AC) deviation range of ±20% of the reference image were considered acceptable. The proposed single-bed scan time reduction was projected to a whole-body examination (patient validation scan) using the continuous-bed-motion mode. RESULTS Sphere and background ACs of 20 kBq/mL and 1 kBq/mL were selected, respectively. The optimized single-bed scan time was approximately 60 s using OSEM-TOF or OSEM-TOF+PSF (four iterations, 4.0-mm Gaussian filter and almost isotropic voxel size of 3.0-mm side length), resulting in a PET spatial resolution of 6.3 mm for OSEM-TOF and 5.5 mm for OSEM-TOF+PSF. In the patient validation, the maximum percentage difference in lesion quantification between standard and optimized protocol (whole-body scan time of 15 vs. 5 min) was below 19%. CONCLUSIONS A reduction of single-bed and whole-body scan time for [68Ga]Ga-PSMA PET/CT compared to current recommended clinical acquisition protocols is postulated. Clinical studies are warranted to validate the applicability of this protocol.
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Affiliation(s)
- Pedro Fragoso Costa
- Department of Nuclear Medicine, Essen University Hospital, Duisburg-Essen University, Essen, Germany -
| | - Walter Jentzen
- Department of Nuclear Medicine, Essen University Hospital, Duisburg-Essen University, Essen, Germany
| | - Finja SÜßELBECK
- Department of Nuclear Medicine, Essen University Hospital, Duisburg-Essen University, Essen, Germany
| | - Wolfgang P Fendler
- Department of Nuclear Medicine, Essen University Hospital, Duisburg-Essen University, Essen, Germany
| | - Christoph Rischpler
- Department of Nuclear Medicine, Essen University Hospital, Duisburg-Essen University, Essen, Germany
| | - Ken Herrmann
- Department of Nuclear Medicine, Essen University Hospital, Duisburg-Essen University, Essen, Germany
| | | | - David Kersting
- Department of Nuclear Medicine, Essen University Hospital, Duisburg-Essen University, Essen, Germany
| | - Manuel Weber
- Department of Nuclear Medicine, Essen University Hospital, Duisburg-Essen University, Essen, Germany
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22
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Advances in Digital PET Technology and Its Potential Impact on Myocardial Perfusion and Blood Flow Quantification. Curr Cardiol Rep 2023; 25:261-268. [PMID: 36826688 DOI: 10.1007/s11886-023-01850-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/06/2023] [Indexed: 02/25/2023]
Abstract
PURPOSE OF REVIEW In this review, we explore the development of digital PET scanners and describe the mechanism by which they work. We dive into some technical details on what differentiates a digital PET from a conventional PET scanner and how such differences lead to better imaging characteristics. Additionally, we summarize the available evidence on the improvements in the images acquired by digital PET as well as the remaining pitfalls. Finally, we report the comparative studies available on how digital PET compares to conventional PET, particularly in the quantification of coronary blood flow. RECENT FINDINGS The advent of digital PET offers high sensitivity and time-of-flight (TOF), which allow lower activity and scan times, with much less risk of detector saturation. This allows faster patient throughput, scanning more patients per generator, and acquiring more consistent image quality across patients. The higher sensitivity captures more of the potential artifacts, particularly motion-related ones, which presents a current challenge that still needs to be tackled. The digital silicon photomultiplier (SiPM) positron emission tomography (PET) machine has been an important development in the technological advancements of non-invasive nuclear cardiovascular imaging. It has enhanced the utility for PET myocardial perfusion imaging (MPI) and myocardial blood flow (MBF) quantification.
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23
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Kiyokawa M, Kang HG, Yamaya T. Tracking the same fast-LGSO crystals by changing surface treatments for better coincidence timing resolution in PET. Biomed Phys Eng Express 2023; 9. [PMID: 36689772 DOI: 10.1088/2057-1976/acb552] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 01/23/2023] [Indexed: 01/24/2023]
Abstract
Achieving fast coincidence timing resolution (CTR) is an important issue in clinical time-of-flight positron emission tomography (TOF-PET) to improve the reconstructed image quality. One of the major factors affecting the CTR is the crystal surface treatment, which is often parameterized as surface roughness. However, previous studies on the crystal surface treatment optimization had two limitations of crystal-by-crystal variation and worse CTR over 200 ps. Here, we report the effects of the crystal surface treatment on the performance of a 20 mm long fast-LGSO crystal based TOF detector by tracking the same crystals in the sub-180 ps CTR regime. The light collection efficiency (LCE), energy resolution (ER) and CTR of the TOF detector were evaluated with six different crystal surface treatments of chemically polished (C.P), C.P half side roughened (1/2S) treatment, and then the C.P one side roughened (1S) treatment, mechanically polished (M.P) treatment, M.P 1/2S treatment, and M.P 1S treatment. The four lateral surfaces of each crystal were wrapped by using enhanced specular reflector film while the top surface was covered by using Teflon tape. The bottom surface of the crystal was optically coupled to a silicon photomultiplier. The timing and energy signals were extracted by using a custom-made high-frequency readout circuit, and then digitized by using a waveform digitizer. All the experimental conditions were same except the crystal surface treatment. Among the six different crystal surface treatments, the M.P 1S would be the optimal crystal surface treatment which balanced enhancements in the CTR (165 ± 3 ps) and ER (10.5 ± 0.5%). Unlike the M.P 1S, the C.P 1S did not enhance the CTR and ER. Hence, the C.P without roughening would be the second-best optimal crystal surface treatment which balanced the CTR (169 ± 3 ps) and ER (10.5 ± 0.5%).
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Affiliation(s)
- Miho Kiyokawa
- National Institutes for Quantum Science and Technology, 4-9-1, Anagawa, Inage-ku, Chiba, Japan.,Department of Medical Engineering, Chiba University, 1-33, Yayoicho, Inage-ku, Chiba, 263-8522, Japan
| | - Han Gyu Kang
- National Institutes for Quantum Science and Technology, 4-9-1, Anagawa, Inage-ku, Chiba, Japan
| | - Taiga Yamaya
- National Institutes for Quantum Science and Technology, 4-9-1, Anagawa, Inage-ku, Chiba, Japan.,Center for Frontier Medical Engineering, Chiba University, 1-33, Yayoicho, Inage-ku, Chiba, 263-8522, Japan
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24
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Mohr P, Efthimiou N, Pagano F, Kratochwil N, Pizzichemi M, Tsoumpas C, Auffray E, Ziemons K. Image Reconstruction Analysis for Positron Emission Tomography With Heterostructured Scintillators. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2023; 7:41-51. [PMID: 37397180 PMCID: PMC10312993 DOI: 10.1109/trpms.2022.3208615] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2023]
Abstract
The concept of structure engineering has been proposed for exploring the next generation of radiation detectors with improved performance. A TOF-PET geometry with heterostructured scintillators with a pixel size of 3.0 × 3.1 × 15 mm3 was simulated using Monte Carlo. The heterostructures consisted of alternating layers of BGO as a dense material with high stopping power and plastic (EJ232) as a fast light emitter. The detector time resolution was calculated as a function of the deposited and shared energy in both materials on an event-by-event basis. While sensitivity was reduced to 32% for 100-μm thick plastic layers and 52% for 50 μm, the coincidence time resolution (CTR) distribution improved to 204 ± 49 and 220 ± 41 ps, respectively, compared to 276 ps that we considered for bulk BGO. The complex distribution of timing resolutions was accounted for in the reconstruction. We divided the events into three groups based on their CTR and modeled them with different Gaussian TOF kernels. On an NEMA IQ phantom, the heterostructures had better contrast recovery in early iterations. On the other hand, BGO achieved a better contrast-to-noise ratio (CNR) after the 15th iteration due to the higher sensitivity. The developed simulation and reconstruction methods constitute new tools for evaluating different detector designs with complex time responses.
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Affiliation(s)
- Philipp Mohr
- Factuly of Chemistry and Biotechnology, FH Aachen University of Applied Sciences, 52428 Jülich, Germany, and also with the Experimental Physics Department, European Organization for Nuclear Research (CERN), 1201 Geneva, Switzerland. He is now with the Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, 9713 GZ Groningen, The Netherlands
| | - Nikos Efthimiou
- Department Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA
| | - Fiammetta Pagano
- Physics Department, University of Milano-Bicocca, 20126 Milan, Italy, and also with the Experimental Physics Department, European Organization for Nuclear Research (CERN), 1201 Geneva, Switzerland
| | - Nicolaus Kratochwil
- Experimental Physics Department, European Organization for Nuclear Research (CERN), 1211 Geneva, Switzerland
| | - Marco Pizzichemi
- Physics Department, University of Milano-Bicocca, 20126 Milan, Italy, and also with the Experimental Physics Department, European Organization for Nuclear Research (CERN), 1201 Geneva, Switzerland
| | - Charalampos Tsoumpas
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, 9713 GZ Groningen, The Netherlands, and also with the Biomedical Imaging Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, LS2 9JT Leeds, U.K
| | - Etiennette Auffray
- Experimental Physics Department, European Organization for Nuclear Research (CERN), 1211 Geneva, Switzerland
| | - Karl Ziemons
- Faculty of Biomedical Engineering and Technomathematics, FH Aachen University of Applied Sciences, 52428 Jülich, Germany
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25
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Li Y, Watanabe M, Isobe T, Ote K, Tokui A, Omura T, Liu H. Simulation study of a brain PET scanner using TOF-DOI detectors equipped with first interaction position detection. Phys Med Biol 2022; 68. [PMID: 36560889 DOI: 10.1088/1361-6560/aca951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 12/06/2022] [Indexed: 12/12/2022]
Abstract
Objective. The aim of this study is to evaluate the performance characteristics of a brain positron emission tomography (PET) scanner composed of four-layer independent read-out time-of-flight depth-of-interaction (TOF-DOI) detectors capable of first interaction position (FIP) detection, using Geant4 application for tomographic emission(GATE). This includes the spatial resolution, sensitivity, count rate capability, and reconstructed image quality.Approach. The proposed TOF-DOI PET detector comprises four layers of a 50 × 50 cerium-doped lutetium-yttrium oxyorthosilicate (LYSO:Ce) scintillator array with 1 mm pitch size, coupled to a 16 × 16 multi-pixel photon counter array with 3.0 mm × 3.0 mm photosensitive segments. Along the direction distant from the center field-of-view (FOV), the scintillator thickness of the four layers is 2.5, 3, 4, and 6 mm. The four layers were simulated with a 150 ps coincidence time resolution and the independent readout make the FIP detection capable. The spatial resolution and imaging performance were compared among the true-FIP, winner-takes-all (WTA) and front-layer FIP (FL-FIP) methods (FL-FIP selects the interaction position located on the front-most interaction layer in all the interaction layers). The National Electrical Manufacturers Association NU 2-2018 procedure was referred and modified to evaluate the performance of proposed scanner.Main results. In detector evaluation, the intrinsic spatial resolutions were 0.52 and 0.76 mm full width at half-maximum (FWHM) at 0° and 30° incidentγ-rays in the first layer pair, respectively. The reconstructed spatial resolution by the filter backprojection (FBP) achieved sub-millimeter FWHM on average over the whole FOV. The maximum true count rate was 207.6 kcps at 15 kBq ml-1and the noise equivalent count rate (NECR_2R) was 54.7 kcps at 6.0 kBq ml-1. Total sensitivity was 45.2 cps kBq-1and 48.4 cps kBq-1at the center and 10 cm off-center FOV, respectively. The TOF and DOI reconstructions significantly improved the image quality in the phantom studies. Moreover, the FL-FIP outperformed the conventional WTA method in terms of the spatial resolution and image quality.Significance. The proposed brain PET scanner could achieve sub-millimeter spatial resolution and high image quality with TOF and DOI reconstruction, which is meaningful to the clinical oncology research. Meanwhile, the comparison among the three positioning methods indicated that the FL-FIP decreased the image degradation caused by Compton scatter more than WTA.
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Affiliation(s)
- Yingying Li
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China.,College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Mitsuo Watanabe
- Central Research Laboratory, Hamamatsu Photonics K. K., Japan
| | - Takashi Isobe
- Central Research Laboratory, Hamamatsu Photonics K. K., Japan
| | - Kibo Ote
- Central Research Laboratory, Hamamatsu Photonics K. K., Japan
| | - Aoi Tokui
- Central Research Laboratory, Hamamatsu Photonics K. K., Japan
| | - Tomohide Omura
- Central Research Laboratory, Hamamatsu Photonics K. K., Japan
| | - Huafeng Liu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China
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26
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Morimoto-Ishikawa D, Hanaoka K, Watanabe S, Yamada T, Yamakawa Y, Minagawa S, Takenouchi S, Ohtani A, Mizuta T, Kaida H, Ishii K. Evaluation of the performance of a high-resolution time-of-flight PET system dedicated to the head and breast according to NEMA NU 2-2012 standard. EJNMMI Phys 2022; 9:88. [PMID: 36525103 PMCID: PMC9758266 DOI: 10.1186/s40658-022-00518-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 12/06/2022] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND This study evaluated the physical performance of a positron emission tomography (PET) system dedicated to the head and breast according to the National Electrical Manufacturers Association (NEMA) NU2-2012 standard. METHODS The spatial resolution, sensitivity, scatter fraction, count rate characteristics, corrections for count losses and randoms, and image quality of the system were determined. All measurements were performed according to the NEMA NU2-2012 acquisition protocols, but image quality was assessed using a brain-sized phantom. Furthermore, scans of the three-dimensional (3D) Hoffmann brain phantom and mini-Derenzo phantom were acquired to allow visual evaluation of the imaging performance for small structures. RESULTS The tangential, radial, and axial full width at half maximum (FWHM) at a 10-mm offset in half the axial field of view were measured as 2.3, 2.5, and 2.9 mm, respectively. The average system sensitivity at the center of the field of view and at a 10-cm radial offset was 7.18 and 8.65 cps/kBq, respectively. The peak noise-equivalent counting rate was 35.2 kcps at 4.8 kBq/ml. The corresponding scatter fraction at the peak noise-equivalent counting rate was 46.8%. The peak true rate and scatter fraction at 8.6 kBq/ml were 127.8 kcps and 54.3%, respectively. The percent contrast value for a 10-mm sphere was approximately 50%. On the 3D Hoffman brain phantom image, the structures of the thin layers composing the phantom were visualized on the sagittal and coronal images. On the mini-Derenzo phantom, each of the 1.6-mm rods was clearly visualized. CONCLUSION Taken together, these results indicate that the head- and breast-dedicated PET system has high resolution and is well suited for clinical PET imaging.
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Affiliation(s)
- Daisuke Morimoto-Ishikawa
- grid.413111.70000 0004 0466 7515Division of Positron Emission Tomography, Institute of Advanced Clinical Medicine, Kindai University Hospital, 377-2 Ohno-Higashi, Osakasayama, Osaka 589-8511 Japan
| | - Kohei Hanaoka
- grid.413111.70000 0004 0466 7515Division of Positron Emission Tomography, Institute of Advanced Clinical Medicine, Kindai University Hospital, 377-2 Ohno-Higashi, Osakasayama, Osaka 589-8511 Japan
| | - Shota Watanabe
- grid.413111.70000 0004 0466 7515Division of Positron Emission Tomography, Institute of Advanced Clinical Medicine, Kindai University Hospital, 377-2 Ohno-Higashi, Osakasayama, Osaka 589-8511 Japan
| | - Takahiro Yamada
- grid.413111.70000 0004 0466 7515Division of Positron Emission Tomography, Institute of Advanced Clinical Medicine, Kindai University Hospital, 377-2 Ohno-Higashi, Osakasayama, Osaka 589-8511 Japan
| | - Yoshiyuki Yamakawa
- grid.274249.e0000 0004 0571 0853Medical Systems Division, Shimadzu Corporation, Kyoto, Japan
| | - Suzuka Minagawa
- grid.274249.e0000 0004 0571 0853Medical Systems Division, Shimadzu Corporation, Kyoto, Japan
| | - Shiho Takenouchi
- grid.274249.e0000 0004 0571 0853Medical Systems Division, Shimadzu Corporation, Kyoto, Japan
| | - Atsushi Ohtani
- grid.274249.e0000 0004 0571 0853Medical Systems Division, Shimadzu Corporation, Kyoto, Japan
| | - Tetsuro Mizuta
- grid.274249.e0000 0004 0571 0853Medical Systems Division, Shimadzu Corporation, Kyoto, Japan
| | - Hayato Kaida
- grid.413111.70000 0004 0466 7515Division of Positron Emission Tomography, Institute of Advanced Clinical Medicine, Kindai University Hospital, 377-2 Ohno-Higashi, Osakasayama, Osaka 589-8511 Japan ,grid.258622.90000 0004 1936 9967Department of Radiology, Kindai University Faculty of Medicine, Osakasayama, Japan
| | - Kazunari Ishii
- grid.413111.70000 0004 0466 7515Division of Positron Emission Tomography, Institute of Advanced Clinical Medicine, Kindai University Hospital, 377-2 Ohno-Higashi, Osakasayama, Osaka 589-8511 Japan ,grid.258622.90000 0004 1936 9967Department of Radiology, Kindai University Faculty of Medicine, Osakasayama, Japan
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27
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Towards high sensitivity and high-resolution PET scanners: imaging-guided proton therapy and total body imaging. BIO-ALGORITHMS AND MED-SYSTEMS 2022. [DOI: 10.2478/bioal-2022-0079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Abstract
Quantitative imaging (i.e., providing not just an image but also the related data) guidance in proton radiation therapy to achieve and monitor the precision of planned radiation energy deposition field in-vivo (a.k.a. proton range verification) is one of the most under-invested aspects of radiation cancer treatment despite that it may dramatically enhance the treatment accuracy and lower the exposure related toxicity improving the entire outcome of cancer therapy. In this article, we briefly describe the effort of the TPPT Consortium (a collaborative effort of groups from the University of Texas and Portugal) on building a time-of-flight positron-emission-tomography (PET) scanner to be used in pre-clinical studies for proton therapy at MD Anderson Proton Center in Houston. We also discuss some related ideas towards improving and expanding the use of PET detectors, including the total body imaging.
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28
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Akamatsu G, Takahashi M, Tashima H, Iwao Y, Yoshida E, Wakizaka H, Kumagai M, Yamashita T, Yamaya T. Performance evaluation of VRAIN: a brain-dedicated PET with a hemispherical detector arrangement. Phys Med Biol 2022; 67. [PMID: 36317319 DOI: 10.1088/1361-6560/ac9e87] [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: 06/03/2022] [Accepted: 10/28/2022] [Indexed: 11/07/2022]
Abstract
Objective.For PET imaging systems, a smaller detector ring enables less intrinsic spatial resolution loss due to the photon non-collinearity effect as well as better balance between production cost and sensitivity, and a hemispherical detector arrangement is more appropriate for brain imaging than a conventional cylindrical arrangement. Therefore, we have developed a brain-dedicated PET system with a hemispherical detector arrangement, which has been commercialized in Japan under the product name of VRAINTM. In this study, we evaluated imaging performance of VRAIN.Approach.The VRAIN used 54 detectors to form the main hemispherical unit and an additional half-ring behind the neck. Each detector was composed of a 12 × 12 array of lutetium fine silicate crystals (4.1 × 4.1 × 10 mm3) and a 12 × 12 array of silicon photomultipliers (4 × 4 mm2active area) with the one-to-one coupling. We evaluated the physical performance of VRAIN according to the NEMA NU 2-2018 standards. Some measurements were modified so as to fit the hemispherical geometry. In addition, we performed18F-FDG imaging in a healthy volunteer.Main results.In the phantom study, the VRAIN showed high resolution for separating 2.2 mm rods, 229 ps TOF resolution and 19% scatter fraction. With the TOF gain for a 20 cm diameter object (an assumed head diameter), the peak noise-equivalent count rate was 144 kcps at 9.8 kBq ml-1and the sensitivity was 25 kcps MBq-1. Overall, the VRAIN provided excellent image quality in phantom and human studies. In the human FDG images, small brain nuclei and gray matter structures were clearly visualized with high contrast and low noise.Significance.We demonstrated the excellent imaging performance of VRAIN, which supported the advantages of the hemispherical detector arrangement.
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Affiliation(s)
- Go Akamatsu
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Sciences, National Institutes for Quantum Science and Technology (QST), Chiba, Japan
| | - Miwako Takahashi
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Sciences, National Institutes for Quantum Science and Technology (QST), Chiba, Japan
| | - Hideaki Tashima
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Sciences, National Institutes for Quantum Science and Technology (QST), Chiba, Japan
| | - Yuma Iwao
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Sciences, National Institutes for Quantum Science and Technology (QST), Chiba, Japan
| | - Eiji Yoshida
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Sciences, National Institutes for Quantum Science and Technology (QST), Chiba, Japan
| | - Hidekatsu Wakizaka
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Sciences, National Institutes for Quantum Science and Technology (QST), Chiba, Japan
| | | | | | - Taiga Yamaya
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Sciences, National Institutes for Quantum Science and Technology (QST), Chiba, Japan
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29
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Sanaat A, Akhavanalaf A, Shiri I, Salimi Y, Arabi H, Zaidi H. Deep-TOF-PET: Deep learning-guided generation of time-of-flight from non-TOF brain PET images in the image and projection domains. Hum Brain Mapp 2022; 43:5032-5043. [PMID: 36087092 PMCID: PMC9582376 DOI: 10.1002/hbm.26068] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 08/18/2022] [Indexed: 11/12/2022] Open
Abstract
We aim to synthesize brain time‐of‐flight (TOF) PET images/sinograms from their corresponding non‐TOF information in the image space (IS) and sinogram space (SS) to increase the signal‐to‐noise ratio (SNR) and contrast of abnormalities, and decrease the bias in tracer uptake quantification. One hundred forty clinical brain 18F‐FDG PET/CT scans were collected to generate TOF and non‐TOF sinograms. The TOF sinograms were split into seven time bins (0, ±1, ±2, ±3). The predicted TOF sinogram was reconstructed and the performance of both models (IS and SS) compared with reference TOF and non‐TOF. Wide‐ranging quantitative and statistical analysis metrics, including structural similarity index metric (SSIM), root mean square error (RMSE), as well as 28 radiomic features for 83 brain regions were extracted to evaluate the performance of the CycleGAN model. SSIM and RMSE of 0.99 ± 0.03, 0.98 ± 0.02 and 0.12 ± 0.09, 0.16 ± 0.04 were achieved for the generated TOF‐PET images in IS and SS, respectively. They were 0.97 ± 0.03 and 0.22 ± 0.12, respectively, for non‐TOF‐PET images. The Bland & Altman analysis revealed that the lowest tracer uptake value bias (−0.02%) and minimum variance (95% CI: −0.17%, +0.21%) were achieved for TOF‐PET images generated in IS. For malignant lesions, the contrast in the test dataset was enhanced from 3.22 ± 2.51 for non‐TOF to 3.34 ± 0.41 and 3.65 ± 3.10 for TOF PET in SS and IS, respectively. The implemented CycleGAN is capable of generating TOF from non‐TOF PET images to achieve better image quality.
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Affiliation(s)
- Amirhossein Sanaat
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland
| | - Azadeh Akhavanalaf
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland
| | - Isaac Shiri
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland
| | - Yazdan Salimi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland
| | - Hossein Arabi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland
| | - Habib Zaidi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland.,Geneva University Neurocenter, Geneva University, Geneva, Switzerland.,Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, Netherlands.,Department of Nuclear Medicine, University of Southern Denmark, Odense, Denmark
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30
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Carra P, Giuseppina Bisogni M, Ciarrocchi E, Morrocchi M, Sportelli G, Rosso V, Belcari N. A neural network-based algorithm for simultaneous event positioning and timestamping in monolithic scintillators. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac72f2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 05/24/2022] [Indexed: 11/11/2022]
Abstract
Abstract
Objective. Monolithic scintillator crystals coupled to silicon photomultiplier (SiPM) arrays are promising detectors for PET applications, offering spatial resolution around 1 mm and depth-of-interaction information. However, their timing resolution has always been inferior to that of pixellated crystals, while the best results on spatial resolution have been obtained with algorithms that cannot operate in real-time in a PET detector. In this study, we explore the capabilities of monolithic crystals with respect to spatial and timing resolution, presenting new algorithms that overcome the mentioned problems. Approach. Our algorithms were tested first using a simulation framework, then on experimentally acquired data. We tested an event timestamping algorithm based on neural networks which was then integrated into a second neural network for simultaneous estimation of the event position and timestamp. Both algorithms are implemented in a low-cost field-programmable gate array that can be integrated in the detector and can process more than 1 million events per second in real-time. Results. Testing the neural network for the simultaneous estimation of the event position and timestamp on experimental data we obtain 0.78 2D FWHM on the (x, y) plane, 1.2 depth-of-interaction FWHM and 156 coincidence time resolution on a
25
mm
×
25
mm
×
8
mm
×
LYSO monolith read-out by 64
3
mm
×
3
mm
Hamamatsu SiPMs. Significance. Our results show that monolithic crystals combined with artificial intelligence can rival pixellated crystals performance for time-of-flight PET applications, while having better spatial resolution and DOI resolution. Thanks to the use of very light neural networks, event characterization can be done on-line directly in the detector, solving the issues of scalability and computational complexity that up to now were preventing the use of monolithic crystals in clinical PET scanners.
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31
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Pourashraf S, Gonzalez-Montoro A, Lee MS, Cates JW, Won JY, Lee JS, Levin CS. Investigation of Electronic Signal Processing Chains for a Prototype TOF-PET System With 100-ps Coincidence Time Resolution. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2022; 6:690-696. [DOI: 10.1109/trpms.2021.3124756] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
| | | | - Min Sun Lee
- Nuclear Emergency and Environmental Protection Division, Korea Atomic Energy Research Institute, Daejeon, Republic of Korea
| | - Joshua W. Cates
- Applied Nuclear Physics Program, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Jun Yeon Won
- Department of Nuclear Medicine and Biomedical Sciences, Seoul National University, Seoul, South Korea
| | - Jae Sung Lee
- Department of Nuclear Medicine and Biomedical Sciences, Seoul National University, Seoul, South Korea
| | - Craig S. Levin
- Department of Radiology, the Department of Bioengineering, the Department of Physics, and the Department of Electrical Engineering, Stanford University, Stanford, CA, USA
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32
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Performance evaluation of dedicated brain PET scanner with motion correction system. Ann Nucl Med 2022; 36:746-755. [PMID: 35698016 DOI: 10.1007/s12149-022-01757-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 05/17/2022] [Indexed: 11/01/2022]
Abstract
OBJECTIVE Various motion correction (MC) algorithms for positron emission tomography (PET) have been proposed to accelerate the diagnostic performance and research in brain activity and neurology. We have incorporated MC system-based optical motion tracking into the brain-dedicated time-of-flight PET scanner. In this study, we evaluate the performance characteristics of the developed PET scanner when performing MC in accordance with the standards and guidelines for the brain PET scanner. METHODS We evaluate the spatial resolution, scatter fraction, count rate characteristics, sensitivity, and image quality of PET images. The MC evaluation is measured in terms of the spatial resolution and image quality that affect movement. RESULTS In the basic performance evaluation, the average spatial resolution by iterative reconstruction was 2.2 mm at 10 mm offset position. The measured peak noise equivalent count rate was 38.0 kcps at 16.7 kBq/mL. The scatter fraction and system sensitivity were 43.9% and 22.4 cps/(Bq/mL), respectively. The image contrast recovery was between 43.2% (10 mm sphere) and 72.0% (37 mm sphere). In the MC performance evaluation, the average spatial resolution was 2.7 mm at 10 mm offset position, when the phantom stage with the point source translates to ± 15 mm along the y-axis. The image contrast recovery was between 34.2 % (10 mm sphere) and 66.8 % (37 mm sphere). CONCLUSIONS The reconstructed images using MC were restored to their nearly identical state as those at rest. Therefore, it is concluded that this scanner can observe more natural brain activity.
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Liu Z, Niu M, Kuang Z, Ren N, Wu S, Cong L, Wang X, Sang Z, Williams C, Yang Y. High resolution detectors for whole-body PET scanners by using dual-ended readout. EJNMMI Phys 2022; 9:29. [PMID: 35445890 PMCID: PMC9023628 DOI: 10.1186/s40658-022-00460-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 04/08/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Most current whole-body positron emission tomography (PET) scanners use detectors with high timing resolution to measure the time-of-flight of two 511 keV photons, improving the signal-to-noise ratio of PET images. However, almost all current whole-body PET scanners use detectors without depth-encoding capability; therefore, their spatial resolution can be affected by the parallax effect. METHODS In this work, four depth-encoding detectors consisting of LYSO arrays with crystals of 2.98 × 2.98 × 20 mm3, 2.98 × 2.98 × 30 mm3, 1.95 × 1.95 × 20 mm3, and 1.95 × 1.95 × 30 mm3, respectively, were read at both ends, with 6 × 6 mm2 silicon photomultiplier (SiPM) pixels in a 4 × 4 array being used. The timing signals of the detectors were processed individually using an ultrafast NINO application-specific integrated circuit (ASIC) to obtain good timing resolution. The 16 energy signals of the SiPM array were read using a row and column summing circuit to obtain four position-encoding energy signals. RESULTS The four PET detectors provided good flood histograms in which all crystals could be clearly resolved, the crystal energy resolutions measured being 10.2, 12.1, 11.4 and 11.7% full width at half maximum (FWHM), at an average crystal depth of interaction (DOI) resolution of 3.5, 3.9, 2.7, and 3.0 mm, respectively. The depth dependence of the timing of each SiPM was measured and corrected, the timing of the two SiPMs being used as the timing of the dual-ended readout detector. The four detectors provided coincidence time resolutions of 180, 214, 239, and 263 ps, respectively. CONCLUSIONS The timing resolution of the dual-ended readout PET detector was approximately 20% better than that of the single-ended readout detector using the same LYSO array, SiPM array, and readout electronics. The detectors developed in this work used long crystals with small cross-sections and provided good flood histograms, DOI, energy, and timing resolutions, suggesting that they could be used to develop whole-body PET scanners with high sensitivity, uniform high spatial resolution, and high timing resolution.
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Affiliation(s)
- Zheng Liu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ming Niu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Zhonghua Kuang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ning Ren
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - San Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Longhan Cong
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Xiaohui Wang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Ziru Sang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Crispin Williams
- European Centre for Nuclear Research (CERN), Geneva, Switzerland
| | - Yongfeng Yang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
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Onishi Y, Hashimoto F, Ote K, Ota R. Unbiased TOF estimation using leading-edge discriminator and convolutional neural network trained by single-source-position waveforms. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac508f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 01/31/2022] [Indexed: 11/12/2022]
Abstract
Abstract
Objective. Convolutional neural networks (CNNs) are a strong tool for improving the coincidence time resolution (CTR) of time-of-flight (TOF) positron emission tomography detectors. However, several signal waveforms from multiple source positions are required for CNN training. Furthermore, there is concern that TOF estimation is biased near the edge of the training space, despite the reduced estimation variance (i.e. timing uncertainty). Approach. We propose a simple method for unbiased TOF estimation by combining a conventional leading-edge discriminator (LED) and a CNN that can be trained with waveforms collected from one source position. The proposed method estimates and corrects the time difference error calculated by the LED rather than the absolute time difference. This model can eliminate the TOF estimation bias, as the combination with the LED converts the distribution of the label data from discrete values at each position into a continuous symmetric distribution. Main results. Evaluation results using signal waveforms collected from scintillation detectors show that the proposed method can correctly estimate all source positions without bias from a single source position. Moreover, the proposed method improves the CTR of the conventional LED. Significance. We believe that the improved CTR will not only increase the signal-to-noise ratio but will also contribute significantly to a part of the direct positron emission imaging.
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Shibuya K, Saito H, Tashima H, Yamaya T. Using inverse Laplace transform in positronium lifetime imaging. Phys Med Biol 2022; 67. [PMID: 35008076 DOI: 10.1088/1361-6560/ac499b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 01/10/2022] [Indexed: 11/11/2022]
Abstract
Positronium (Ps) lifetime imaging is gaining attention to bring out additional biomedical information from positron emission tomography (PET). The lifetime of Psin vivocan change depending on the physical and chemical environments related to some diseases. Due to the limited sensitivity, Ps lifetime imaging may require merging some voxels for statistical accuracy. This paper presents a method for separating the lifetime components in the voxel to avoid information loss due to averaging. The mathematics for this separation is the inverse Laplace transform (ILT), and the authors examined an iterative numerical ILT algorithm using Tikhonov regularization, namely CONTIN, to discriminate a small lifetime difference due to oxygen saturation. The separability makes it possible to merge voxels without missing critical information on whether they contain abnormally long or short lifetime components. The authors conclude that ILT can compensate for the weaknesses of Ps lifetime imaging and extract the maximum amount of information.
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Affiliation(s)
- Kengo Shibuya
- Institute of Physics, Graduate School of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan.,Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan
| | - Haruo Saito
- Institute of Physics, Graduate School of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan
| | - Hideaki Tashima
- Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan
| | - Taiga Yamaya
- Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan
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Akamatsu G, Shimada N, Matsumoto K, Daisaki H, Suzuki K, Watabe H, Oda K, Senda M, Terauchi T, Tateishi U. New standards for phantom image quality and SUV harmonization range for multicenter oncology PET studies. Ann Nucl Med 2022; 36:144-161. [PMID: 35029817 DOI: 10.1007/s12149-021-01709-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 12/05/2021] [Indexed: 11/01/2022]
Abstract
Not only visual interpretation for lesion detection, staging, and characterization, but also quantitative treatment response assessment are key roles for 18F-FDG PET in oncology. In multicenter oncology PET studies, image quality standardization and SUV harmonization are essential to obtain reliable study outcomes. Standards for image quality and SUV harmonization range should be regularly updated according to progress in scanner performance. Accordingly, the first aim of this study was to propose new image quality reference levels to ensure small lesion detectability. The second aim was to propose a new SUV harmonization range and an image noise criterion to minimize the inter-scanner and intra-scanner SUV variabilities. We collected a total of 37 patterns of images from 23 recent PET/CT scanner models using the NEMA NU2 image quality phantom. PET images with various acquisition durations of 30-300 s and 1800 s were analyzed visually and quantitatively to derive visual detectability scores of the 10-mm-diameter hot sphere, noise-equivalent count (NECphantom), 10-mm sphere contrast (QH,10 mm), background variability (N10 mm), contrast-to-noise ratio (QH,10 mm/N10 mm), image noise level (CVBG), and SUVmax and SUVpeak for hot spheres (10-37 mm diameters). We calculated a reference level for each image quality metric, so that the 10-mm sphere can be visually detected. The SUV harmonization range and the image noise criterion were proposed with consideration of overshoot due to point-spread function (PSF) reconstruction. We proposed image quality reference levels as follows: QH,10 mm/N10 mm ≥ 2.5 and CVBG ≤ 14.1%. The 10th-90th percentiles in the SUV distributions were defined as the new SUV harmonization range. CVBG ≤ 10% was proposed as the image noise criterion, because the intra-scanner SUV variability significantly depended on CVBG. We proposed new image quality reference levels to ensure small lesion detectability. A new SUV harmonization range (in which PSF reconstruction is applicable) and the image noise criterion were also proposed for minimizing the SUV variabilities. Our proposed new standards will facilitate image quality standardization and SUV harmonization of multicenter oncology PET studies. The reliability of multicenter oncology PET studies will be improved by satisfying the new standards.
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Affiliation(s)
- Go Akamatsu
- National Institutes for Quantum Science and Technology (QST), 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
| | - Naoki Shimada
- Cancer Institute Hospital, 3-8-31 Ariake, Koto, Tokyo, 135-8550, Japan.
| | - Keiichi Matsumoto
- Kyoto College of Medical Science, 1-3 Imakita, Oyamahigashi-cho, Sonobe-cho, Nantan, Kyoto, 622-0041, Japan
| | - Hiromitsu Daisaki
- Gunma Prefectural College of Health Sciences, 323-1 Kamioki-machi, Maebashi, Gunma, 371-0052, Japan
| | - Kazufumi Suzuki
- Dokkyo Medical University Hospital, 880 Kitakobayashi, Mibu, Shimotsugagun, Tochigi, 321-0293, Japan
| | - Hiroshi Watabe
- Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8578, Japan
| | - Keiichi Oda
- Hokkaido University of Science, 7-Jo 15-4-1 Maeda, Teine, Sapporo, Hokkaido, 006-8585, Japan
| | - Michio Senda
- Kobe City Medical Center General Hospital, 2-1-1 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Takashi Terauchi
- Cancer Institute Hospital, 3-8-31 Ariake, Koto, Tokyo, 135-8550, Japan
| | - Ukihide Tateishi
- Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
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van Sluis J, Brouwers AH, Boellaard R, Noordzij W. Digital PET systems. Nucl Med Mol Imaging 2022. [DOI: 10.1016/b978-0-12-822960-6.00131-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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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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Abstract
Abstract
In this partial review and partial attempt at vision of what may be the future of dedicated brain PET scanners, the key implementations of the PET technique, we postulate that we are still on a development path and there is still a lot to be done in order to develop optimal brain imagers. Optimized for particular imaging tasks and protocols, and also mobile, that can be used outside the PET center, in addition to the expected improvements in sensitivity and resolution. For this multi-application concept to be more practical, flexible, adaptable designs are preferred. This task is greatly facilitated by the improved TOF performance that allows for more open, adjustable, limited angular coverage geometries without creating image artifacts. As achieving uniform very high resolution in the whole body is not practical due to technological limits and high costs, hybrid systems using a moderate-resolution total body scanner (such as J-PET) combined with a very high performing brain imager could be a very attractive approach. As well, as using magnification inserts in the total body or long-axial length imagers to visualize selected targets with higher resolution. In addition, multigamma imagers combining PET with Compton imaging should be developed to enable multitracer imaging.
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The effect of modern PET technology and techniques on the EANM paediatric dosage card. Eur J Nucl Med Mol Imaging 2021; 49:1964-1969. [PMID: 34910233 PMCID: PMC9016049 DOI: 10.1007/s00259-021-05635-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/24/2021] [Indexed: 11/08/2022]
Abstract
Aim Recent advancements in PET technology have brought with it significant improvements in PET performance and image quality. In particular, the extension of the axial field of view of PET systems, and the introduction of semiconductor technology into the PET detector, initially for PET/MR, and more recently available long-field-of-view PET/CT systems (≥ 25 cm) have brought a step change improvement in the sensitivity of PET scanners. Given the requirement to limit paediatric doses, this increase in sensitivity is extremely welcome for the imaging of children and young people. This is even more relevant with PET/MR, where the lack of CT exposures brings further dose reduction benefits to this population. In this short article, we give some details around the benefits around new PET technology including PET/MR and its implications on the EANM paediatric dosage card. Material and methods Reflecting on EANM adult guidance on injected activities, and making reference to bed overlap and the concept of MBq.min bed−1 kg−1, we use published data on image quality from PET/MR systems to update the paediatric dosage card for PET/MR and extended axial field of view (≥ 25 cm) PET/CT systems. However, this communication does not cover the expansion of paediatric dosing for the half-body and total-body scanners that have recently come to market. Results In analogy to the existing EANM dosage card, new parameters for the EANM paediatric dosage card were developed (class B, baseline value: 10.7 MBq, minimum recommended activity 10 MBq). The recommended administered activities for the systems considered in this communication range from 11 MBq [18F]FDG for a child with a weight of 3 kg to 149 MBq [18F]FDG for a paediatric patient weight of 68 kg, assuming a scan of 3 min per bed position. The mean effective dose over all ages (1 year and older) is 2.85 mSv. Conclusion With this, recommendations for paediatric dosing are given for systems that have not been considered previously.
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Miller K. A backprojection kernel (KRNL3D) for very-wide-aperture 3D tomography applied to PET with Multigrid for precise use of time-of-flight data. Phys Med Biol 2021; 66. [PMID: 34673567 DOI: 10.1088/1361-6560/ac320a] [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: 04/29/2021] [Accepted: 10/21/2021] [Indexed: 11/11/2022]
Abstract
In 'KRNL3D' we derive a kernel functionK(y1,y2,φ) whose backprojections from all directions (θ,φ) in the spherical band∣φ∣<φ¯maxon the celestial sphere, when integrated with respect to solid angle, yieldρ, the 3D Gaussian point response function (PRF) of radius 1. ThisK, when convolved against line integral data from an unknown density functionf, yields an integral formula for the 'mollification'ff=ρ∗f, which is a slightly blurred version off, and which stabilizes the mild ill-posedness. Applied to positron emission tomography that backprojection reconstruction occurs stochastically and one emission event at a time, after needed data corrections. We describe Octave (≈Matlab) codes to tabulateKand to test its use with a large apertureφ¯max=π/3orπ/6. 'KRNL3D-TOF' truncates backprojection to a cylindrical patch about the TOF approximate location of each event. These 'backplacements' decrease the computational cost and limit noise and streaking in one region from contaminating the reconstruction in more distant regions. They also retain the ability to count emission events in an isolated blob despiteverylow event counts, a valuable feature fordynamicstudies of metabolic processes. 'Multigrid' allows further reduction in the radius and lengths of the cylinders, thereby enabling even moreprecise use of the TOF information. This precision should be especially important as researchers decrease the TOF uncertainty in newer generation scanners. Finally, we discuss 'further work' that needs to be done. Our codes are being made freely available athttps://github.com/keithmillerberkeley/PET-codes.
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Affiliation(s)
- Keith Miller
- Department of Mathematics, University of California at Berkeley, Berkeley, CA 94720-3840, United States of America
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Teimoorisichani M, Panin V, Rothfuss H, Sari H, Rominger A, Conti M. A CT-less approach to quantitative PET imaging using the LSO intrinsic radiation for long-axial FOV PET scanners. Med Phys 2021; 49:309-323. [PMID: 34818446 PMCID: PMC9299938 DOI: 10.1002/mp.15376] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 11/10/2021] [Accepted: 11/11/2021] [Indexed: 11/11/2022] Open
Abstract
Purpose Long‐axial field‐of‐view (FOV) positron emission tomography (PET) scanners have gained a lot of interest in the recent years. Such scanners provide increased sensitivity and enable unique imaging opportunities that were not previously feasible. Benefiting from the high sensitivity of a long‐axial FOV PET scanner, we studied a computed tomography (CT)–less reconstruction algorithm for the Siemens Biograph Vision Quadra with an axial FOV of 106 cm. Methods In this work, the background radiation from radioisotope lutetium‐176 in the scintillators was used to create an initial estimate of the attenuation maps. Then, joint activity and attenuation reconstruction algorithms were used to create an improved attenuation map of the object. The final attenuation maps were then used to reconstruct quantitative PET images, which were compared against CT‐based PET images. The proposed method was evaluated on data from three patients who underwent a flurodeoxyglucouse PET scan. Results Segmentation of the PET images of the three studied patients showed an average quantitative error of 6.5%–8.3% across all studied organs when using attenuation maps from maximum likelihood estimation of attenuation and activity and 5.3%–6.6% when using attenuation maps from maximum likelihood estimation of activity and attenuation correction coefficients. Conclusions Benefiting from the background radiation of lutetium‐based scintillators, a quantitative CT‐less PET imaging technique was evaluated in this work.
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Affiliation(s)
| | - Vladimir Panin
- Siemens Medical Solutions USA, Inc., Knoxville, Tennessee, USA
| | - Harold Rothfuss
- Siemens Medical Solutions USA, Inc., Knoxville, Tennessee, USA
| | - Hasan Sari
- Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland.,Department of Nuclear Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Axel Rominger
- Department of Nuclear Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Maurizio Conti
- Siemens Medical Solutions USA, Inc., Knoxville, Tennessee, USA
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Laforest R, Khalighi M, Natsuaki Y, Rajagopal A, Chandramohan D, Byrd D, An H, Larson P, James SS, Sunderland JJ, Kinahan PE, Hope TA. Harmonization of PET image reconstruction parameters in simultaneous PET/MRI. EJNMMI Phys 2021; 8:75. [PMID: 34739621 PMCID: PMC8571452 DOI: 10.1186/s40658-021-00416-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Accepted: 10/01/2021] [Indexed: 01/17/2023] Open
Abstract
Objective Simultaneous PET/MRIs vary in their quantitative PET performance due to inherent differences in the physical systems and differences in the image reconstruction implementation. This variability in quantitative accuracy confounds the ability to meaningfully combine and compare data across scanners. In this work, we define image reconstruction parameters that lead to comparable contrast recovery curves across simultaneous PET/MRI systems. Method The NEMA NU-2 image quality phantom was imaged on one GE Signa and on one Siemens mMR PET/MRI scanner. The phantom was imaged at 9.7:1 contrast with standard spheres (diameter 10, 13, 17, 22, 28, 37 mm) and with custom spheres (diameter: 8.5, 11.5, 15, 25, 32.5, 44 mm) using a standardized methodology. Analysis was performed on a 30 min listmode data acquisition and on 6 realizations of 5 min from the listmode data. Images were reconstructed with the manufacturer provided iterative image reconstruction algorithms with and without point spread function (PSF) modeling. For both scanners, a post-reconstruction Gaussian filter of 3–7 mm in steps of 1 mm was applied. Attenuation correction was provided from a scaled computed tomography (CT) image of the phantom registered to the MR-based attenuation images and verified to align on the non-attenuation corrected PET images. For each of these image reconstruction parameter sets, contrast recovery coefficients (CRCs) were determined for the SUVmean, SUVmax and SUVpeak for each sphere. A hybrid metric combining the root-mean-squared discrepancy (RMSD) and the absolute CRC values was used to simultaneously optimize for best match in CRC between the two scanners while simultaneously weighting toward higher resolution reconstructions. The image reconstruction parameter set was identified as the best candidate reconstruction for each vendor for harmonized PET image reconstruction. Results The range of clinically relevant image reconstruction parameters demonstrated widely different quantitative performance across cameras. The best match of CRC curves was obtained at the lowest RMSD values with: for CRCmean, 2 iterations-7 mm filter on the GE Signa and 4 iterations-6 mm filter on the Siemens mMR, for CRCmax, 4 iterations-6 mm filter on the GE Signa, 4 iterations-5 mm filter on the Siemens mMR and for CRCpeak, 4 iterations-7 mm filter with PSF on the GE Signa and 4 iterations-7 mm filter on the Siemens mMR. Over all reconstructions, the RMSD between CRCs was 1.8%, 3.6% and 2.9% for CRC mean, max and peak, respectively. The solution of 2 iterations-3 mm on the GE Signa and 4 iterations-3 mm on Siemens mMR, both with PSF, led to simultaneous harmonization and with high CRC and low RMSD for CRC mean, max and peak with RMSD values of 2.8%, 5.8% and 3.2%, respectively. Conclusions For two commercially available PET/MRI scanners, user-selectable parameters that control iterative updates, image smoothing and PSF modeling provide a range of contrast recovery curves that allow harmonization in harmonization strategies of optimal match in CRC or high CRC values. This work demonstrates that nearly identical CRC curves can be obtained on different commercially available scanners by selecting appropriate image reconstruction parameters. Supplementary Information The online version contains supplementary material available at 10.1186/s40658-021-00416-0.
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Affiliation(s)
- Richard Laforest
- Mallinckrodt Institute of Radiology, Washington University, St. Louis, MO, USA.
| | - Mehdi Khalighi
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Yutaka Natsuaki
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | - Abhejit Rajagopal
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Dharshan Chandramohan
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | | | - Hongyu An
- Mallinckrodt Institute of Radiology, Washington University, St. Louis, MO, USA
| | - Peder Larson
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Sara St James
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | | | | | - Thomas A Hope
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
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Akerele MI, Karakatsanis NA, Forsythe RO, Dweck MR, Syed M, Aykroyd RG, Sourbron S, Newby DE, Tsoumpas C. Iterative reconstruction incorporating background correction improves quantification of [ 18F]-NaF PET/CT images of patients with abdominal aortic aneurysm. J Nucl Cardiol 2021; 28:1875-1886. [PMID: 31721093 PMCID: PMC8648624 DOI: 10.1007/s12350-019-01940-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 10/16/2019] [Indexed: 12/20/2022]
Abstract
BACKGROUND A confounding issue in [18F]-NaF PET/CT imaging of abdominal aortic aneurysms (AAA) is the spill in contamination from the bone into the aneurysm. This study investigates and corrects for this spill in contamination using the background correction (BC) technique without the need to manually exclude the part of the AAA region close to the bone. METHODS Seventy-two (72) datasets of patients with AAA were reconstructed with the standard ordered subset expectation maximization (OSEM) algorithm incorporating point spread function (PSF) modelling. The spill in effect in the aneurysm was investigated using two target regions of interest (ROIs): one covering the entire aneurysm (AAA), and the other covering the aneurysm but excluding the part close to the bone (AAAexc). ROI analysis was performed by comparing the maximum SUV in the target ROI (SUVmax(T)), the corrected cSUVmax (SUVmax(T) - SUVmean(B)) and the target-to-blood ratio (TBR = SUVmax(T)/SUVmean(B)) with respect to the mean SUV in the right atrium region. RESULTS There is a statistically significant higher [18F]-NaF uptake in the aneurysm than normal aorta and this is not correlated with the aneurysm size. There is also a significant difference in aneurysm uptake for OSEM and OSEM + PSF (but not OSEM + PSF + BC) when quantifying with AAA and AAAexc due to the spill in from the bone. This spill in effect depends on proximity of the aneurysms to the bone as close aneurysms suffer more from spill in than farther ones. CONCLUSION The background correction (OSEM + PSF + BC) technique provided more robust AAA quantitative assessments regardless of the AAA ROI delineation method, and thus it can be considered as an effective spill in correction method for [18F]-NaF AAA studies.
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Affiliation(s)
- Mercy I Akerele
- Biomedical Imaging Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, LS2 9NL, UK
| | - Nicolas A Karakatsanis
- Division of Radiopharmaceutical Sciences, Department of Radiology, Weil Cornell Medical College of Cornell University, New York, NY, USA
| | - Rachael O Forsythe
- British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
- Edinburgh Imaging Facility, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Marc R Dweck
- British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
- Edinburgh Imaging Facility, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Maaz Syed
- British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
- Edinburgh Imaging Facility, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | | | - Steven Sourbron
- Biomedical Imaging Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, LS2 9NL, UK
| | - David E Newby
- Edinburgh Imaging Facility, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Charalampos Tsoumpas
- Biomedical Imaging Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, LS2 9NL, UK.
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Uenomachi M, Takahashi M, Shimazoe K, Takahashi H, Kamada K, Orita T, Ogane K, Tsuji AB. Simultaneous in vivo imaging with PET and SPECT tracers using a Compton-PET hybrid camera. Sci Rep 2021; 11:17933. [PMID: 34504184 PMCID: PMC8429650 DOI: 10.1038/s41598-021-97302-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 08/24/2021] [Indexed: 01/11/2023] Open
Abstract
Positron-emission tomography (PET) and single-photon-emission computed tomography (SPECT) are well-established nuclear-medicine imaging methods used in modern medical diagnoses. Combining PET with 18F-fluorodeoxyglucose (FDG) and SPECT with an 111In-labelled ligand provides clinicians with information about the aggressiveness and specific types of tumors. However, it is difficult to integrate a SPECT system with a PET system because SPECT requires a collimator. Herein, we describe a novel method that provides simultaneous imaging with PET and SPECT nuclides by combining PET imaging and Compton imaging. The latter is an imaging method that utilizes Compton scattering to visualize gamma rays over a wide range of energies without requiring a collimator. Using Compton imaging with SPECT nuclides, instead of the conventional SPECT imaging method, enables PET imaging and Compton imaging to be performed with one system. In this research, we have demonstrated simultaneous in vivo imaging of a tumor-bearing mouse injected with 18F-FDG and an 111In-antibody by using a prototype Compton-PET hybrid camera. We have succeeded in visualizing accumulations of 18F-FDG and 111In-antibody by performing PET imaging and Compton imaging simultaneously. As simultaneous imaging utilizes the same coordinate axes, it is expected to improve the accuracy of diagnoses.
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Affiliation(s)
- Mizuki Uenomachi
- Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan
| | - Miwako Takahashi
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Inage, Chiba, Chiba, Japan
| | - Kenji Shimazoe
- Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan. .,JST, PRESTO, Saitama, 332-0012, Japan.
| | - Hiroyuki Takahashi
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, 2-11-16, Yayoi, Bunkyo-ku, Tokyo, Japan
| | - Kei Kamada
- Tohoku University, 2-1-1, Katahira, Sendai, Miyagi, Japan
| | - Tadashi Orita
- Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Kashiwa, Chiba, Japan
| | - Kenichiro Ogane
- Department of Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan.,Department of Nuclear Medicine, International University of Health and Welfare, 1-4-3, Minato-ku, Tokyo, Japan
| | - Atsushi B Tsuji
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Inage, Chiba, Chiba, Japan
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Watanabe M, Moriya T, Uchida H, Omura T. Simulation study of potential time-of-flight capabilities for a multilayer DOI-PET detector with an independent readout structure. Phys Med Biol 2021; 66. [PMID: 34293731 DOI: 10.1088/1361-6560/ac16e7] [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: 06/21/2021] [Accepted: 07/22/2021] [Indexed: 11/11/2022]
Abstract
A multilayer depth-of-interaction positron emission tomography (DOI-PET) detector with an independent readout structure has a potential advantage as a time-of-flight (TOF)-PET detector. The thin scintillator block of each detector layer can afford an improved coincidence time resolution (CTR) of ∼100 ps because the photon transfer time spread within the scintillator inherently decreases. To evaluate the potential TOF capabilities of a multilayer DOI-PET detector, which consists of thin layers of a cerium-doped lutetium-yttrium oxyorthosilicate (LYSO:Ce) scintillator coupled to a multi-pixel photon counter (MPPC) array, we examined the detector's CTR performance via Monte Carlo simulations. We used several types of scintillator structures: a monolithic plate, laser-processing array with 3.2 mm pitch, fine laser-processing array with 1.6 mm pitch, and pixelated array with 3.2 mm pitch, with 2, 4, 6, and 8 mm thickness values of a 25.6 mm × 25.6 mm scintillator cross-section. The MPPC array was composed of 3.0 mm × 3.0 mm photosensitive segments arranged in an 8 × 8 array. Here, we note that the CTR performance also significantly depends on the timing detection method, which generates a timing trigger signal for coincidence detection. Thus, we evaluated the CTRs for each scintillator structure by adopting four timing detection methods: using the total sum signal of 64 MPPC chips (T_sum), the maximum signal in the 64 MPPC chips (Max), the sum signal of a partial number of MPPC chips located at and in the vicinity of theγ-ray interaction position (P_sum), and the average of the timestamps generated at several MPPC chips (Ave). When using the T_sum for timing detection, the CTR full width at half-maximum values were ∼100 ps regardless of the scintillator structure. However, when using the Max signal approach, the CTRs of the monolithic plates, laser-processing arrays, and fine-pitch laser-processing arrays were drastically degraded with increasing thickness. On the other hand, the CTRs of the pixelated arrays exhibited almost no degradation. To improve the CTRs of the monolithic plate and the (fine-pitch) laser-processing array that exhibit a large light spread in the scintillator block, we applied the P_sum and Ave methods. The resulting CTRs significantly improved upon using P_sum; however, in the Ave approach the improvement effect disappeared when the thickness was <6 mm in case of our simulation.
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Affiliation(s)
- Mitsuo Watanabe
- Central Research Laboratory, Hamamatsu Photonics K. K., Hamamatsu, Japan
| | - Takahiro Moriya
- Central Research Laboratory, Hamamatsu Photonics K. K., Hamamatsu, Japan
| | - Hiroshi Uchida
- Global Strategic Challenge Center, Hamamatsu Photonics K. K., Hamamatsu, Japan
| | - Tomohide Omura
- Central Research Laboratory, Hamamatsu Photonics K. K., Hamamatsu, Japan
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Toussaint M, Lecomte R, Dussault JP. Improvement of Spatial Resolution with Iterative PET Reconstruction using UltraFast TOF. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2021; 5:729-737. [PMID: 35059544 PMCID: PMC8765719 DOI: 10.1109/trpms.2020.3033561] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2023]
Abstract
The impact of Time-of-Flight (TOF) on positron emission tomography (PET) spatial resolution is generally considered negligible. In this work, a two-step approach based on simulations of two-dimensional scanner configurations is taken to show that ultra-fast TOF has the potential to overcome the limitation induced by the physical size of detectors on spatial resolution. An estimation of the lower bound on spatial resolution using point sources is provided, followed by a qualitative assessment of the resolution obtained using a Hot Spot phantom. The impact of detector width, TOF resolution and TOF binning on the achieved spatial resolution is also studied. While gain beyond the expected blur due to detector size is demonstrated, the detector size remains one limiting factor albeit less prominent. The dependence on acquisition statistics to reach the full potential of TOF-induced gain in spatial resolution is demonstrated. A simulated brain phantom acquired with a fictive three-dimensional PET scanner was qualitatively analyzed and structures smaller than the typical limit are clearly made visible by reconstructing the images with a ∼13-ps TOF resolution. A potential application of this feature of ultra-fast TOF would be the design of clinical PET scanners achieving spatial resolution beyond the current state-of-the-art.
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Affiliation(s)
- Maxime Toussaint
- Department of Computer Science, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Roger Lecomte
- Sherbrooke Molecular Imaging Center of CRCHUS and Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Jean-Pierre Dussault
- Department of Computer Science, Université de Sherbrooke, Sherbrooke, QC, Canada
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Akamatsu G, Takyu S, Yoshida E, Iwao Y, Tashima H, Nishikido F, Yamaya T. Evaluation of a Hamamatsu TOF-PET Detector Module With 3.2-mm Pitch LFS Scintillators and a 256-Channel SiPM Array. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2021. [DOI: 10.1109/trpms.2020.3035876] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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LaBella A, Tavernier S, Woody C, Purschke M, Zhao W, Goldan AH. Toward 100 ps Coincidence Time Resolution Using Multiple Timestamps in Depth-Encoding PET Modules: A Monte Carlo Simulation Study. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2021. [DOI: 10.1109/trpms.2020.3043691] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Park K, Jung J, Choi Y, Leem H, Kim Y. Feasibility Study of a Time-of-Flight Brain Positron Emission Tomography Employing Individual Channel Readout Electronics. SENSORS 2021; 21:s21165566. [PMID: 34451008 PMCID: PMC8402256 DOI: 10.3390/s21165566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Revised: 08/13/2021] [Accepted: 08/15/2021] [Indexed: 11/16/2022]
Abstract
The purpose of this study was to investigate the feasibility of a time-of-flight (TOF) brain positron emission tomography (PET) providing high-quality images. It consisted of 30 detector blocks arranged in a ring with a diameter of 257 mm and an axial field of view of 52.2 mm. Each detector block was composed of two detector modules and two application-specific integrated circuit (ASIC) chips. The detector module was composed of an 8 × 8 array of 3 × 3 mm2 multi-pixel photon counters and an 8 × 8 array of 3.11 × 3.11 × 15 mm3 lutetium yttrium oxyorthosilicate scintillators. The 64-channel individual readout ASIC was used to acquire the position, energy, and time information of a detected gamma ray. A coincidence timing resolution of 187 ps full width at half maximum (FWHM) was achieved using a pair of channels of two detector modules. The energy resolution and spatial resolution were 6.6 ± 0.6% FWHM (without energy nonlinearity correction) and 2.5 mm FWHM, respectively. The results of this study demonstrate that the developed TOF brain PET could provide excellent performance, allowing for a reduction in radiation dose or scanning time for brain imaging due to improved sensitivity and signal-to-noise ratio.
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