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Pommranz CM, Schmidt FP, Mannheim JG, Diebold SJ, Tenzer C, Santangelo A, Pichler BJ. Design and performance simulation studies of a breast PET insert integrable into a clinical whole-body PET/MRI scanner. Phys Med Biol 2023; 68. [PMID: 36753773 DOI: 10.1088/1361-6560/acba77] [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: 09/01/2022] [Accepted: 02/08/2023] [Indexed: 02/10/2023]
Abstract
Objective. Three different breast positron emission tomography (PET) insert geometries are proposed for integration into an existing magnetic resonance imaging (MRI) breast coil (Breast Biopsy Coil, NORAS MRI products) to be used inside a whole-body PET/MRI scanner (Biograph mMR, Siemens Healthineers) to enhance the sensitivity and spatial resolution of imaging inside the breast.Approach. Monte Carlo simulations were performed to predict and compare the performance characteristics of the three geometries in terms of the sensitivity, spatial resolution, scatter fraction, and noise equivalent count rate (NECR). In addition, the background single count rate due to organ uptake in a clinical scan scenario was predicted using a realistic anthropomorphic phantom.Main results. In the center of the field of view (cFOV), absolute sensitivities of 3.1%, 2.7%, and 2.2% were found for Geometry A (detectors arranged in two cylinders), Geometry B (detectors arranged in two partial cylinders), and Geometry C (detectors arranged in two half cylinders combined with two plates), respectively. The full width at half maximum spatial resolution was determined to be 1.7 mm (Geometry A), 1.8 mm (Geometry B) and 2.0 mm (Geometry C) at 5 mm from the cFOV. Designs with multiple scintillation-crystal layers capable of determining the depth of interaction (DOI) strongly improved the spatial resolution at larger distances from the transaxial cFOV. The system scatter fractions were 33.1% (Geometries A and B) and 32.3% (Geometry C). The peak NECRs occurred at source activities of 300 MBq (Geometry A), 310 MBq (Geometry B) and 340 MBq (Geometry C). The background single-event count rates were 17.1 × 106cps (Geometry A), 15.3 × 106cps (Geometry B) and 14.8 × 106cps (Geometry C). Geometry A in the three-layer DOI variant exhibited the best PET performance characteristics but could be challenging to manufacture. Geometry C had the lowest impact on the spatial resolution and the lowest sensitivity among the investigated geometries.Significance. Geometry B in the two-layer DOI variant represented an effective compromise between the PET performance and manufacturing difficulty and was found to be a promising candidate for the future breast PET insert.
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Affiliation(s)
- C M Pommranz
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tuebingen, Roentgenweg 13, D-72076 Tuebingen, Germany.,Institute for Astronomy and Astrophysics, Eberhard Karls University Tuebingen, Sand 1, D-72076 Tuebingen, Germany
| | - F P Schmidt
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tuebingen, Roentgenweg 13, D-72076 Tuebingen, Germany.,Department of Nuclear Medicine and Clinical Molecular Imaging, University Hospital Tuebingen, Otfried-Mueller-Strasse 14, D-72076 Tuebingen, Germany
| | - J G Mannheim
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tuebingen, Roentgenweg 13, D-72076 Tuebingen, Germany.,Cluster of Excellence iFIT (EXC 2180) Image Guided and Functionally Instructed Tumor Therapies, University of Tuebingen, Tuebingen, Germany
| | - S J Diebold
- Institute for Astronomy and Astrophysics, Eberhard Karls University Tuebingen, Sand 1, D-72076 Tuebingen, Germany
| | - C Tenzer
- Institute for Astronomy and Astrophysics, Eberhard Karls University Tuebingen, Sand 1, D-72076 Tuebingen, Germany
| | - A Santangelo
- Institute for Astronomy and Astrophysics, Eberhard Karls University Tuebingen, Sand 1, D-72076 Tuebingen, Germany
| | - B J Pichler
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tuebingen, Roentgenweg 13, D-72076 Tuebingen, Germany.,Cluster of Excellence iFIT (EXC 2180) Image Guided and Functionally Instructed Tumor Therapies, University of Tuebingen, Tuebingen, Germany
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Kang HG, Tashima H, Nishikido F, Akamatsu G, Wakizaka H, Higuchi M, Yamaya T. Initial results of a mouse brain PET insert with a staggered 3-layer DOI detector. Phys Med Biol 2021; 66. [PMID: 34666328 DOI: 10.1088/1361-6560/ac311c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/19/2021] [Indexed: 11/11/2022]
Abstract
Objective.Small animal positron emission tomography (PET) requires a submillimeter resolution for better quantification of radiopharmaceuticals. On the other hand, depth-of-interaction (DOI) information is essential to preserve the spatial resolution while maintaining the sensitivity. Recently, we developed a staggered 3-layer DOI detector with 1 mm crystal pitch and 15 mm total crystal thickness, but we did not demonstrate the imaging performance of the DOI detector with full ring geometry. In this study we present initial imaging results obtained for a mouse brain PET prototype developed with the staggered 3-layer DOI detector.Approach.The prototype had 53 mm inner diameter and 11 mm axial field-of-view. The PET scanner consisted of 16 DOI detectors each of which had a staggered 3-layer LYSO crystal array (4/4/7 mm) coupled to a 4 × 4 silicon photomultiplier array. The physical performance was evaluated in terms of the NEMA NU 4 2008 protocol.Main Results.The measured spatial resolutions at the center and 15 mm radial offset were 0.67 mm and 1.56 mm for filtered-back-projection, respectively. The peak absolute sensitivity of 0.74% was obtained with an energy window of 400-600 keV. The resolution phantom imaging results show the clear identification of a submillimetric rod pattern with the ordered-subset expectation maximization algorithm. The inter-crystal scatter rejection using a narrow energy window could enhance the resolvability of a 0.75 mm rod significantly.Significance.In an animal imaging experiment, the detailed mouse brain structures such as cortex and thalamus were clearly identified with high contrast. In conclusion, we successfully developed the mouse brain PET insert prototype with a staggered 3-layer DOI detector.
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Affiliation(s)
- Han Gyu Kang
- National Institutes for Quantum Science and Technology (QST), 4-9-1, Anagawa, Inage-ku, Chiba, Japan
| | - Hideaki Tashima
- National Institutes for Quantum Science and Technology (QST), 4-9-1, Anagawa, Inage-ku, Chiba, Japan
| | - Fumihiko Nishikido
- National Institutes for Quantum Science and Technology (QST), 4-9-1, Anagawa, Inage-ku, Chiba, Japan
| | - Go Akamatsu
- National Institutes for Quantum Science and Technology (QST), 4-9-1, Anagawa, Inage-ku, Chiba, Japan
| | - Hidekazu Wakizaka
- National Institutes for Quantum Science and Technology (QST), 4-9-1, Anagawa, Inage-ku, Chiba, Japan
| | - Makoto Higuchi
- National Institutes for Quantum Science and Technology (QST), 4-9-1, Anagawa, Inage-ku, Chiba, Japan
| | - Taiga Yamaya
- National Institutes for Quantum Science and Technology (QST), 4-9-1, Anagawa, Inage-ku, Chiba, Japan
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Zhang X, Yu H, Xie Q, Xie S, Ye B, Guo M, Zhao Z, Huang Q, Xu J, Peng Q. Design study of a PET detector with 0.5 mm crystal pitch for high-resolution preclinical imaging. Phys Med Biol 2021; 66. [PMID: 34130263 DOI: 10.1088/1361-6560/ac0b82] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 06/15/2021] [Indexed: 11/12/2022]
Abstract
Preclinical positron emission tomography (PET) is a sensitive and quantitative molecule imaging modality widely used in characterizing the biological processes and diseases in small animals. The purpose of this study is to investigate the methods to optimize a PET detector for high-resolution preclinical imaging. The PET detector proposed in this study consists of a 28 × 28 array of LYSO crystals 0.5 × 0.5 × 6.25 mm3in size, a wedged lightguide, and a 6 × 6 array of SiPMs 3 × 3 mm2in size. The simulation results showed that the most uniform flood map was achieved when the thickness of the lightguide was 2.35 mm. The quality of the flood map was significantly improved by suppressing the electronics noises using the simple threshold method with a best threshold. The peak-to-valley ratio of flood map improved 25.4% when the algorithm of ICS rejection was applied. An energy resolution (12.96% ± 1.03%) was measured on the prototype scanner constructed with 12 proposed detectors. Lastly, a prototype preclinic PET imager was constructed with 12 optimized detectors. The point source experiment was performed and an excellent spatial resolution (axial: 0.56 mm, tangential: 0.46 mm, radial: 0.42 mm) was achieved with the proposed high-performance PET detectors.
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Affiliation(s)
- Xi Zhang
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Hongsen Yu
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Qiangqiang Xie
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Siwei Xie
- Institute of Biomedical Engineering Shenzhen Bay Laboratory, Shenzhen, 518132, People's Republic of China
| | - Baihezi Ye
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Minghao Guo
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, People's Republic of China
| | - Zhixiang Zhao
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, People's Republic of China
| | - Qiu Huang
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, People's Republic of China
| | - Jianfeng Xu
- School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Qiyu Peng
- Institute of Biomedical Engineering Shenzhen Bay Laboratory, Shenzhen, 518132, People's Republic of China
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Prout DL, Gu Z, Shustef M, Chatziioannou AF. A digital phoswich detector using time-over-threshold for depth of interaction in PET. Phys Med Biol 2020; 65:245017. [PMID: 33202397 PMCID: PMC8382115 DOI: 10.1088/1361-6560/abcb21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We present the performance of a digital phoswich positron emission tomography (PET) detector, composed by layers of pixilated scintillator arrays, read out by solid state light detectors and an application specific integrated circuit (ASIC). We investigated the use of integrated charge from the scintillation pulses along with time-over-threshold (ToT) to determine the layer of interaction (DOI) in the scintillator. Simulations were performed to assess the effectiveness of the ToT measurements for separating the scintillator events and identifying cross-layer-crystal-scatter (CLCS) events. These simulations indicate that ToT and charge integration from such a detector provide sufficient information to determine the layer of interaction. To demonstrate this in practice, we used a pair of prototype LYSO/BGO detectors. One detector consisted of a 19 × 19 array of 7 mm long LYSO crystals (1.36 mm pitch) coupled to a 16 × 16 array of 8 mm long BGO crystals (1.63 mm pitch). The other detector was similar except the LYSO crystal pitch was 1.63 mm. These detectors were coupled to an 8 × 8 multi-pixel photon counter mounted on a PETsys TOFPET2 ASIC. This high performance ASIC provided digital readout of the integrated charge and ToT from these detectors. We present a method to separate the events from the two scintillator layers using the ToT, and also investigate the performance of this detector. All the crystals within the proposed detector were clearly resolved, and the peak to valley ratio was 11.8 ± 4.0 and 10.1 ± 2.9 for the LYSO and BGO flood images. The measured energy resolution was 9.9% ± 1.3% and 28.5% ± 5.0% respectively for the LYSO and BGO crystals in the phoswich layers. The timing resolution between the LYSO-LYSO, LYSO-BGO and BGO-BGO coincidences was 468 ps, 1.33 ns and 2.14 ns respectively. Results show ToT can be used to identify the crystal layer where events occurred and also identify and reject the majority of CLCS events between layers.
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Affiliation(s)
- David L Prout
- Crump Institute for Molecular Imaging, David Geffen School of Medicine, University of California, Los Angeles, CA, United States of America
- Shared first authorship
| | - Zheng Gu
- Crump Institute for Molecular Imaging, David Geffen School of Medicine, University of California, Los Angeles, CA, United States of America
- Institute of Biomedical Engineering, Shenzhen Bay Laboratory, Shenzhen, Guangdong Province, People's Republic of China
- Shared first authorship
| | - Max Shustef
- Crump Institute for Molecular Imaging, David Geffen School of Medicine, University of California, Los Angeles, CA, United States of America
| | - Arion F Chatziioannou
- Crump Institute for Molecular Imaging, David Geffen School of Medicine, University of California, Los Angeles, CA, United States of America
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