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Choi CH, Felder J, Lerche C, Shah NJ. MRI Coil Development Strategies for Hybrid MR-PET Systems: A Review. IEEE Rev Biomed Eng 2024; 17:342-350. [PMID: 37015609 DOI: 10.1109/rbme.2022.3227337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Simultaneously operating MR-PET systems have the potential to provide synergetic multi-parametric information, and, as such, interest surrounding their use and development is increasing. However, despite the potential advantages offered by fully combined MR-PET systems, implementing this hybrid integration is technically laborious, and any factors degrading the quality of either modality must be circumvented to ensure optimal performance. In order to attain the best possible quality from both systems, most full MR-PET integrations tend to place the shielded PET system inside the MRI system, close to the target volume of the subject. The radiofrequency (RF) coil used in MRI systems is a key factor in determining the quality of the MR images, and, in simultaneous acquisition, it is generally positioned inside the PET system and PET imaging region, potentially resulting in attenuation and artefacts in the PET images. Therefore, when designing hybrid MR-PET systems, it is imperative that consideration be given to the RF coils inside the PET system. In this review, we present current state-of-the-art RF coil designs used for hybrid MR-PET experiments and discuss various design strategies for constructing PET transparent RF coils.
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Sang Z, Kuang Z, Wang X, Ren N, Wu S, Niu M, Cong L, Liu Z, Hu Z, Sun T, Liang D, Liu X, Zheng H, Li Y, Yang Y. Mutual interferences between SIAT aPET insert and a 3 T uMR 790 MRI scanner. Phys Med Biol 2023; 68. [PMID: 36549011 DOI: 10.1088/1361-6560/acae17] [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: 08/09/2022] [Accepted: 12/22/2022] [Indexed: 12/24/2022]
Abstract
Objective.Dual-modality small animal PET/MR imaging provides temporally correlated information on two biochemical processes of a living object. An magnetic resonance imaging (MRI)-compatible small animal PET insert named Shenzhen Institutes of Advanced Technology (SIAT) aPET was developed by using dual-ended readout depth encoding detectors to simultaneously achieve a uniform high spatial resolution and high sensitivity at the SIAT. In this work, the mutual interferences between SIAT aPET and the 3 T uMR 790 MRI scanner of United Imaging was quantitatively evaluated.Approach.To minimize the mutual interferences, only the PET detectors and the readout electronics were placed inside the MRI scanner, the major signal processing electronic was placed in the corner of the MRI room and the auxiliary unit was placed in the MRI technical room. A dedicated mouse radio fRequency (RF) coil with a transmitter and receiver was developed for the PET insert. The effects of PET scanner on theB0andB1field of the MRI scanner and the quality of the MRI images were measured. The effects of MRI imaging on the performance of both the PET detectors and scanner were also measured.Main results.The electronic and mechanical components of the PET insert affected the homogeneity of theB0field. The PET insert had no effect on the homogeneity ofB1produced by the dedicated mouse coil but slightly reduced the strength ofB1. The mean and standard deviation of the RF noise map were increased by 2.2% and 11.6%, respectively, while the PET insert was placed in the MRI scanner and powered on. Eddy current was produced while the PET insert was placed in the MRI scanner, and it was further increased while the PET insert was powered on. Despite the above-mentioned interferences from the PET insert, the MR images of a uniform cylindrical water phantom showed that the changes in the signal-to-noise ratio (SNR) and homogeneity as the PET insert was placed in the MRI scanner were acceptable regardless of whether the PET insert was powered off or powered on. The maximum reduction of SNR was less than 11%, and the maximum reduction of homogeneity was less than 2.5% while the PET insert was placed inside the MRI scanner and powered on for five commonly used MRI sequences. MRI using gradient echo (GRE), spin echo (SE) and fast spin echo (FSE) sequences had negligible effects on the flood histograms and energy resolution of the PET detectors, as well as the spatial resolution and sensitivity of the PET scanner.Significance.The mutual interference between the SIAT aPET and the 3 T uMR 790 MRI scanner are acceptable. Simultaneous PET/MRI imaging of small animals can be performed with the two scanners.
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Affiliation(s)
- Ziru Sang
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Zhonghua Kuang
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
| | - Xiaohui Wang
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Ning Ren
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - San Wu
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Ming Niu
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Longhan Cong
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Zheng Liu
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Zhanli Hu
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Tao Sun
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Dong Liang
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Xin Liu
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Hairong Zheng
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Ye Li
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
| | - Yongfeng Yang
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People's Republic of China
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Nakajima S, Fushimi Y, Hinoda T, Sakata A, Okuchi S, Arakawa Y, Ishimori T, Nakamoto Y. Brain imaging of sequential acquisition using a flexible PET scanner and 3-T MRI: quantitative and qualitative assessment. Ann Nucl Med 2022; 37:209-218. [PMID: 36585566 DOI: 10.1007/s12149-022-01817-6] [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: 09/15/2022] [Accepted: 12/23/2022] [Indexed: 01/01/2023]
Abstract
OBJECTIVE A mobile PET scanner termed flexible PET (fxPET) has been designed to fit existing MRI systems. The purpose of this study was to assess brain imaging with fxPET combined with 3-T MRI in comparison with conventional PET (cPET)/CT. METHODS In this prospective study, 29 subjects with no visible lesions except for mild leukoaraiosis on whole brain imaging underwent 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) cPET/CT followed by fxPET and MRI. The registration differences between fxPET and MRI and between cPET and CT were compared by measuring spatial coordinates. Three-dimensional magnetization-prepared rapid acquisition gradient-echo T1-weighted imaging (T1WI) was acquired. We applied two methods of attenuation correction to the fxPET images: MR-based attenuation correction, which yielded fxPETMRAC; and CT-based attenuation correction, which yielded fxPETCTAC. The three PET datasets were co-registered to the T1WI. Following subcortical segmentation and cortical parcellation, volumes of interest were placed in each PET image to assess physiological accumulation in the brain. SUVmean was obtained and compared between the three datasets. We also visually evaluated image distortion and clarity of fxPETMRAC. RESULTS Mean misregistration of fxPET/MRI was < 3 mm for each margin. Mean registration differences were significantly larger for fxPET/MRI than for cPET/CT except for the superior margin. There were high correlations between the three PET datasets regarding SUVmean. On visual evaluation of image quality, the grade of distortion was comparable between fxPETMRAC and cPET, and the grade of clarity was acceptable but inferior for fxPETMRAC compared with cPET. CONCLUSIONS fxPET could successfully determine physiological [18F]FDG uptake; however, improved image clarity is desirable. In this study, fxPET/MRI at 3-T was feasible for brain imaging.
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Affiliation(s)
- Satoshi Nakajima
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Yasutaka Fushimi
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.
| | - Takuya Hinoda
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Akihiko Sakata
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Sachi Okuchi
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Yoshiki Arakawa
- Department of Neurosurgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takayoshi Ishimori
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Yuji Nakamoto
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
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Hunter WCJ, DeWitt DQ, Miyaoka RS. Performance Characteristics of a Dual-Sided Position-Sensitive Sparse-Sensor Detector for Gamma-ray Imaging. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2022; 6:385-392. [PMID: 35372738 PMCID: PMC8974312 DOI: 10.1109/trpms.2021.3087465] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Purpose We characterize the performance of a dualsided position-sensitive sparse sensor (DS-PS3) array detector for positron emission tomography (PET). The DS-PS3 detector is designed as a high performance, cost effective PET detector for organ-specific imaging systems (e.g., brain, breast, etc.). Methods Two sparse 4-by-4 arrays of silicon photomultipliers (18.5% SiPM fill-factor) coupled through segmented light guide are used to readout a 15-by-15 array of 2-mm-pitch, 20-mm-long LSYO crystals. Uniform flood data were used for crystal identification, depth determination, and position-dependent energy resolution. Intrinsic-spatial and depth-of-interaction (DOI) resolutions were determined by stepping a collimated gamma-ray source over the front and side, respectively. Results We measured an average intrinsic spatial resolution of 2.14 ± 0.07 mm full width at half maximum (FWHM). DOI FWHM resolution varied from 2.2 mm for crystals over sensors to 5.3 mm for crystals between sensors. Average DOI resolution was 3.6 ± 0.8 mm FHWM. Average energy resolution for the detector module was 16.6% with a range of 11.3% to 25.8%. Conclusions We have demonstrated use of a dual-sided sparse sensor arrays to enable low-cost high-performance decoding of three-dimensional positioning within a PET detector using an 18.5% sensor fill-factor.
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Leem H, Choi Y, Jung J, Park K, Kim Y, Jung JH. Optimized TOF-PET detector using scintillation crystal array for brain imaging. NUCLEAR ENGINEERING AND TECHNOLOGY 2022. [DOI: 10.1016/j.net.2022.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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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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Lee JS, Kim KM, Choi Y, Kim HJ. A Brief History of Nuclear Medicine Physics, Instrumentation, and Data Sciences in Korea. Nucl Med Mol Imaging 2021; 55:265-284. [PMID: 34868376 DOI: 10.1007/s13139-021-00721-7] [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: 07/19/2021] [Revised: 10/14/2021] [Accepted: 10/18/2021] [Indexed: 10/19/2022] Open
Abstract
We review the history of nuclear medicine physics, instrumentation, and data sciences in Korea to commemorate the 60th anniversary of the Korean Society of Nuclear Medicine. In the 1970s and 1980s, the development of SPECT, nuclear stethoscope, and bone densitometry systems, as well as kidney and cardiac image analysis technology, marked the beginning of nuclear medicine physics and engineering in Korea. With the introduction of PET and cyclotron in Korea in 1994, nuclear medicine imaging research was further activated. With the support of large-scale government projects, the development of gamma camera, SPECT, and PET systems was carried out. Exploiting the use of PET scanners in conjunction with cyclotrons, extensive studies on myocardial blood flow quantification and brain image analysis were also actively pursued. In 2005, Korea's first domestic cyclotron succeeded in producing radioactive isotopes, and the cyclotron was provided to six universities and university hospitals, thereby facilitating the nationwide supply of PET radiopharmaceuticals. Since the late 2000s, research on PET/MRI has been actively conducted, and the advanced research results of Korean scientists in the fields of silicon photomultiplier PET and simultaneous PET/MRI have attracted significant attention from the academic community. Currently, Korean researchers are actively involved in endeavors to solve a variety of complex problems in nuclear medicine using artificial intelligence and deep learning technologies.
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Affiliation(s)
- Jae Sung Lee
- Department of Nuclear Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080 Korea
| | - Kyeong Min Kim
- Department of Isotopic Drug Development, Korea Radioisotope Center for Pharmaceuticals, Korea Institute of Radiological and Medical Sciences, Seoul, Korea
| | - Yong Choi
- Department of Electronic Engineering, Sogang University, Seoul, Korea
| | - Hee-Joung Kim
- Department of Radiological Science, Yonsei University, Wonju, Korea
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Kim Y, Choi Y, Kim KB, Leem H, Jung JH. Serial line multiplexing method based on bipolar pulse for PET. NUCLEAR ENGINEERING AND TECHNOLOGY 2021. [DOI: 10.1016/j.net.2021.05.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Domínguez-Jiménez DY, Alva-Sánchez H. Energy spectra due to the intrinsic radiation of LYSO/LSO scintillators for a wide range of crystal sizes. Med Phys 2021; 48:1596-1607. [PMID: 33475160 DOI: 10.1002/mp.14729] [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: 08/04/2020] [Revised: 10/22/2020] [Accepted: 12/21/2020] [Indexed: 01/02/2023] Open
Abstract
PURPOSE Most detectors in current positron emission tomography (PET) scanners and prototypes use lutetium oxyorthosilicate (LSO) or lutetium yttrium oxyorthosilicate (LYSO) scintillators. The aim of this work is to provide a complete set of background energy spectra, due to the scintillator intrinsic radioactivity, for a wide range of crystal sizes. METHODS An analytical model, developed and validated in a previous work, was used to obtain the background energy spectra of square base cuboids of different dimensions. The model uses the photon absorption probabilities of the three gamma rays (88, 202, and 307 keV) emitted following the beta decay of 176 Lu to 176 Hf excited states. These probabilities were obtained for each crystal size considered in this work from Monte Carlo simulations using the PENELOPE code. The probabilities are then used to normalize and shift the beta spectrum to the corresponding energy value of the simultaneous detection of one, two, or three gamma rays in the scintillator. The simulated cuboids had side lengths of 5, 10, 20, 30, 40, 50, and 60 mm and crystal thickness T = 2.5, 5, 10, 15, and 20 mm. From these results a complete set of energy spectra, including intermediate dimensions, were obtained. In addition, LYSO and LSO were compared in terms of their analytical background energy spectra for two crystal sizes. The analytical spectra were convolved using a variable Gaussian kernel to account for the energy resolution of a typical detector. A parameterization of the photon absorption probabilities for each gamma ray energy as a function of the cuboid volume to surface area ratio was obtained. RESULTS A data set of L(Y)SO background energy spectra was obtained and is available for the reader as 2D histograms. The model accurately predicts the structure of the energy spectra including the relative peak and valley intensities. The data allow visualizing how the structure evolves with increasing crystal length and thickness. Lutetium yttrium oxyorthosilicate and LSO present very similar background energy spectra for the range of sizes studied in this work and therefore the data generated can be confidently used for both scintillator materials. The filtered spectra showed a variable shift in the main peaks, depending on crystal size, alerting that to achieve a correct detector calibration using the background spectrum is not straight forward and requires precise data analysis and measurements. In addition, we found that square base L(Y)SO cuboids with same volume to surface area ratio have background spectra with the same structure. CONCLUSIONS We present the energy spectra of L(Y)SO crystal of different sizes which will be very useful for industry and research groups developing and simulating detectors for positron imaging applications in terms of calibration, quality assurance, crystal maps, detector fine gain tuning, background reduction and other applications using the long-lived 176 Lu source. We analyzed the data produced in this work and found that crystal cuboids with equal volume to surface area ratio produce the same background energy spectra, a conclusion that simplifies its calculation and clarifies why the same energy spectrum is observed under different experimental setups.
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Affiliation(s)
| | - Héctor Alva-Sánchez
- Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, Mexico City, 01000, Mexico
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Suzuki M, Fushimi Y, Okada T, Hinoda T, Nakamoto R, Arakawa Y, Sawamoto N, Togashi K, Nakamoto Y. Quantitative and qualitative evaluation of sequential PET/MRI using a newly developed mobile PET system for brain imaging. Jpn J Radiol 2021; 39:669-680. [PMID: 33641056 DOI: 10.1007/s11604-021-01105-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 02/15/2021] [Indexed: 10/22/2022]
Abstract
PURPOSE To evaluate the clinical feasibility of a newly developed mobile PET system with MR-compatibility (flexible PET; fxPET), compared with conventional PET (cPET)/CT for brain imaging. METHODS Twenty-one patients underwent cPET/CT with subsequent fxPET/MRI using 18F-FDG. As qualitative evaluation, we visually rated image quality of MR and PET images using a four-point scoring system. We evaluated overall image quality for MR, while we evaluated overall image quality, sharpness and lesion contrast. As quantitative evaluation, we compared registration accuracy between two modalities [(fxPET and MRI) and (cPET and CT)] measuring spatial coordinates. We also examined the accuracy of regional 18F-FDG uptake. RESULTS All acquired images were of diagnostic quality and the number of detected lesions did not differ significantly between fxPET/MR and cPET/CT. Mean misregistration was significantly larger with fxPET/MRI than with cPET/CT. SUVmax and SUVmean for fxPET and cPET showed high correlations in the lesions (R = 0.84, 0.79; P < 0.001, P = 0.002, respectively). In normal structures, we also showed high correlations of SUVmax (R = 0.85, 0.87; P < 0.001, P < 0.001, respectively) and SUVmean (R = 0.83, 0.87; P < 0.001, P < 0.001, respectively) in bilateral caudate nuclei and a moderate correlation of SUVmax (R = 0.65) and SUVmean (R = 0.63) in vermis. CONCLUSIONS The fxPET/MRI system showed image quality within the diagnostic range, registration accuracy below 3 mm and regional 18F-FDG uptake highly correlated with that of cPET/CT.
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Affiliation(s)
- Mizue Suzuki
- Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Yasutaka Fushimi
- Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.
| | - Tomohisa Okada
- Human Brain Research Center, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Takuya Hinoda
- Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Ryusuke Nakamoto
- Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Yoshiki Arakawa
- Department of Neurosurgery, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Nobukatsu Sawamoto
- Department of Human Health Sciences, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Kaori Togashi
- Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Yuji Nakamoto
- Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
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Application of sigmoidal optimization to reconstruct nuclear medicine image: Comparison with filtered back projection and iterative reconstruction method. NUCLEAR ENGINEERING AND TECHNOLOGY 2021. [DOI: 10.1016/j.net.2020.06.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Yang HJ, Yoon DK, Suh TS. Sensing changes in tumor during boron neutron capture therapy using PET with a collimator: Simulation study. NUCLEAR ENGINEERING AND TECHNOLOGY 2020. [DOI: 10.1016/j.net.2020.02.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Gundacker S, Heering A. The silicon photomultiplier: fundamentals and applications of a modern solid-state photon detector. ACTA ACUST UNITED AC 2020; 65:17TR01. [DOI: 10.1088/1361-6560/ab7b2d] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Kim MS, Shin HB, Choi MG, Monzen H, Shim JG, Suh TS, Yoon DK. Reference based simulation study of detector comparison for BNCT-SPECT imaging. NUCLEAR ENGINEERING AND TECHNOLOGY 2020. [DOI: 10.1016/j.net.2019.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Abstract
Field Programmable Gate Array (FPGA) is a general purpose programmable logic device that can be configured by a customer after manufacturing to perform from a simple logic gate operations to complex systems on chip or even artificial intelligence systems. Scientific publications related to FPGA started in 1992 and, up to now, we found more than 70,000 documents in the two leading scientific databases (Scopus and Clarivative Web of Science). These publications show the vast range of applications based on FPGAs, from the new mechanism that enables the magnetic suspension system for the kilogram redefinition, to the Mars rovers’ navigation systems. This paper reviews the top FPGAs’ applications by a scientometric analysis in ScientoPy, covering publications related to FPGAs from 1992 to 2018. Here we found the top 150 applications that we divided into the following categories: digital control, communication interfaces, networking, computer security, cryptography techniques, machine learning, digital signal processing, image and video processing, big data, computer algorithms and other applications. Also, we present an evolution and trend analysis of the related applications.
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Gonzalez AJ, Pincay EJ, Canizares G, Lamprou E, Sanchez S, Catret JV, Jimenez-Serrano S, Cabello J, Schwaiger M, Iborra A, Merlin T, Gonzalez-Montoro A, Visvikis D, Benlloch JM, Vidal LF, Barbera J, Aussenhofer S, Hernandez L, Moliner L, Sanchez F, Correcher C. Initial Results of the MINDView PET Insert Inside the 3T mMR. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2019. [DOI: 10.1109/trpms.2018.2866899] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Lee JS, Kovalski G, Sharir T, Lee DS. Advances in imaging instrumentation for nuclear cardiology. J Nucl Cardiol 2019; 26:543-556. [PMID: 28718074 DOI: 10.1007/s12350-017-0979-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2017] [Accepted: 06/08/2017] [Indexed: 12/22/2022]
Abstract
Advances in imaging instrumentation and technology have greatly contributed to nuclear cardiology. Dedicated cardiac SPECT cameras incorporating novel, highly efficient detector, collimator, and system designs have emerged with the expansion of nuclear cardiology. Solid-state radiation detectors incorporating cadmium zinc telluride, which directly convert radiation to electrical signals and yield improved energy resolution and spatial resolution and enhanced count sensitivity geometries, are increasingly gaining favor as the detector of choice for application in dedicated cardiac SPECT systems. Additionally, hybrid imaging systems in which SPECT and PET are combined with X-ray CT are currently widely used, with PET/MRI hybrid systems having also been recently introduced. The improved quantitative SPECT/CT has the potential to measure the absolute quantification of myocardial blood flow and flow reserve. Rapid development of silicon photomultipliers leads to enhancement in PET image quality and count rates. In addition, the reduction of emission-transmission mismatch artifacts via application of accurate time-of-flight information, and cardiac motion de-blurring aided by anatomical images, are emerging techniques for further improvement of cardiac PET. This article reviews recent advances such as these in nuclear cardiology imaging instrumentation and technology, and the corresponding diagnostic benefits.
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Affiliation(s)
- Jae Sung Lee
- Department of Nuclear Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Korea
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea
| | | | - Tali Sharir
- Department of Nuclear Cardiology, Assuta Medical Centers, 96 Igal Alon, C Building, 67891, Tel Aviv, Israel.
- Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
| | - Dong Soo Lee
- Department of Nuclear Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Korea.
- Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Suwon, Korea.
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Moghadam N, Espagnet R, Bouchard J, Lecomte R, Fontaine R. Studying the effects of metallic components of PET-insert on PET and MRI performance due to gradient switching. Phys Med Biol 2019; 64:075003. [PMID: 30695769 DOI: 10.1088/1361-6560/ab0291] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Inserting positron emission tomography (PET) detection modules inside an MRI bore imposes extra challenges owing to the behavior of metallic materials in a strong magnetic field. The metallic parts even when placed outside an MRI field of view may not only disturb MRI performance, but could also increase temperature and vibrations, leading to premature failure of PET electronics. To investigate the compatibility of detection modules inside 3 T, 7 T and 9.4 T MRI bore, a theoretical study of the metal induced artifacts originating from component materials of electronic circuit is presented. The LabPET II detection module and a modified version of it in which the connector was replaced by ball grid array (BGA) were studied. In addition, the effect of eddy current and the associated heat loss on the PET detection module have been examined using COMSOL Multiphysics® simulations for 10 kHz and 100 kHz gradient switching. Results show that displacement artifacts resulting from the presence of small amounts of ferromagnetic metal and the heating effects of metal due to gradient switching can be compensated by using the slightly modified LabPET II detection module. Thus, the LabPET II system would be MR-compatible with some minor adjustments to operate effectively inside an MRI bore without interfering with its performance.
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Affiliation(s)
- Narjes Moghadam
- Groupe de Recherche en Appareillage Médical de Sherbrooke (GRAMS), Interdisciplinary Institute for Technological Innovation (3IT), Department of Electrical and Computer Engineering, Université de Sherbrooke, Sherbrooke, Québec, Canada
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Lee S, Choi Y, Jung JH, Jung J, Kim KB, Choe HJ, Leem HT, Lee H, Huh YM. Performance evaluation of a small animal PET scanner a high level of multiplexing and charge-signal transmission. Phys Med Biol 2019; 64:045015. [PMID: 30650398 DOI: 10.1088/1361-6560/aafeff] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Small animal positron emission tomography (PET) is a noninvasive imaging modality that enables in vivo imaging and quantification of the biological processes of small experimental animals. We have developed a small animal PET that utilizes a high-resolution multiplexed readout and charge signal transmission (CST) method. The small animal PET was composed of six detector blocks consisting of SiPMs and LYSO arrays. Six detector blocks were mounted on a PET gantry having an inner diameter of 76 mm, outer diameter of 112 mm, and axial length of 40.8 mm. The charge signals of SiPM output were transmitted to the input of multiplexed readout using 4 m flexible flat cables. The multiplexed readout was composed of six main boards, each of which included 36 detector boards, to reduce the number of readout channels by a factor of 36, with a multiplexing ratio of 144:4. The performance of the small animal PET was evaluated using NEMA NU 4-2008 standards, and its imaging capability was demonstrated by in vivo mouse imaging studies. The average energy and time resolutions were 13.2% ± 0.3% and 3.8 ns, respectively. The spatial resolution at the center of the transaxial FOV was 1.1 mm, and the peak sensitivity at the center of the axial FOV was 1.5%. The peak noise equivalent count (NEC) rate and scatter fraction were 21.1 kcps at 18.2 MBq and 21%, respectively. The acquired images demonstrated high quality tracer uptake patterns of small experimental animals. The results of performance evaluation and animal imaging indicate that the small animal PET developed in this study can provide high-quality small animal imaging with cost-effectiveness and compactness.
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Affiliation(s)
- Sangwon Lee
- Molecular Imaging Research and Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul 04107, Republic of Korea
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Lim KT, Kim H, Kim M, Kim Y, Lee CY, Cho G. Photon-number resolving capability in SiPMs with electric field variation for radiation detection applications. Radiat Phys Chem Oxf Engl 1993 2019. [DOI: 10.1016/j.radphyschem.2018.05.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Lee BJ, Watkins RD, Lee KS, Chang CM, Levin CS. Performance evaluation of RF coils integrated with an RF-penetrable PET insert for simultaneous PET/MRI. Magn Reson Med 2018; 81:1434-1446. [PMID: 30260501 DOI: 10.1002/mrm.27444] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 05/01/2018] [Accepted: 06/11/2018] [Indexed: 01/19/2023]
Abstract
PURPOSE An "RF-penetrable" PET insert that allows the MR body coil to be used for RF transmission was developed to make it easier for an existing MR center to achieve simultaneous PET/MRI. This study focuses on experiments and analyses to study PET/RF coil configurations for simultaneous PET/MR studies. METHODS To investigate the appropriate RF coil design, a transmit/receive (TX/RX) birdcage coil and an RX-only phased-array coil (TX from body coil), both fitting inside the PET ring were built and characterized. For MR performance evaluation, B1 field uniformity and MR image SNR were calculated. PET photon attenuation due to each coil was studied by means of CT-based attenuation maps and reconstructed PET images. RESULTS When using the RX-only phased-array coil (TX from body coil), compared with the TX/RX birdcage coil, the B1 field uniformity and the MR image (gradient echo and fast spin echo) SNR increased by 2.4±4.8%, 386.1±62.3%, and 205.0±56.5%, respectively. Although some components of the coil were distributed within the PET FOV, no significant PET photon attenuation was shown in the CT-based attenuation map and reconstructed PET images. CONCLUSION RF coil configurations for an RF-penetrable PET insert for simultaneous PET/MRI were studied. The RX-only phased-array coil (TX from body coil) outperformed the TX/RX birdcage coil with improved MR performance as well as negligible PET photon attenuation.
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Affiliation(s)
- Brian J Lee
- Department of Radiology, Stanford University, Stanford, California
- Department of Mechanical Engineering, Stanford University, Stanford, California
| | - Ronald D Watkins
- Department of Radiology, Stanford University, Stanford, California
| | - Keum Sil Lee
- Department of Radiology, Stanford University, Stanford, California
| | - Chen-Ming Chang
- Department of Radiology, Stanford University, Stanford, California
- Department of Applied Physics, Stanford University, Stanford, California
| | - Craig S Levin
- Department of Radiology, Stanford University, Stanford, California
- Department of Bioengineering, Stanford University, Stanford, California
- Department of Electrical Engineering, Stanford University, Stanford, California
- Department of Physics, Stanford University, Stanford, California
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Raylman RR, Ledden P, Stolin AV, Hou B, Jaliparthi G, Martone PF. Small animal, positron emission tomography-magnetic resonance imaging system based on a clinical magnetic resonance imaging scanner: evaluation of basic imaging performance. J Med Imaging (Bellingham) 2018; 5:033504. [PMID: 30840723 DOI: 10.1117/1.jmi.5.3.033504] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 08/14/2018] [Indexed: 11/14/2022] Open
Abstract
Development of advanced preclinical imaging techniques has had an important impact on the field of biomedical research, with positron emission tomography (PET) imaging the most mature of these efforts. Developers of preclinical PET scanners have joined the recent multimodality imaging trend by combining PET imaging with other modalities, such as magnetic resonance imaging (MRI). Our group has developed a combined PET-MRI insert for the imaging of animals up to the size of rats in a clinical 3T MRI scanner. The system utilizes a sequential scanner configuration instead of the more common coplanar geometry. The PET component of the system consists of a ring of 12 liquid-cooled, SiPM-based detector modules ( diameter = 15.2 cm ). System performance was evaluated with the NEMA NU 4-2008 protocol. Spatial resolution is ∼ 1.71 mm 5 cm from the center of the field-of-view measured from single-slice rebinned filtered backprojection-reconstructed images. Peak noise equivalent count rate is 17.7 kcps at 8.5 MBq; peak sensitivity is 2.9%. The MRI component of the system is composed of a 12-cm-diameter birdcage transmit/receive coil with a dual-preamplifier interface possessing very low noise preamplifiers. System performance was evaluated using American College of Radiology-based methods. Image homogeneity is 99%; the ghosting ratio is 0.0054. The signal-to-noise ratio is 95 and spatial resolution is ∼ 0.25 mm . There was no discernable cross-modality interference.
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Affiliation(s)
- Raymond R Raylman
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
| | - Patrick Ledden
- Nova Medical Inc., Wilmington, Massachusetts, United States
| | - Alexander V Stolin
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
| | - Bob Hou
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
| | - Ganghadar Jaliparthi
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
| | - Peter F Martone
- West Virginia University, Center for Advanced Imaging, Department of Radiology, Morgantown, West Virginia, United States
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Gonzalez AJ, Sanchez F, Benlloch JM. Organ-Dedicated Molecular Imaging Systems. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2018. [DOI: 10.1109/trpms.2018.2846745] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Akram MSH, Levin CS, Obata T, Hirumi G, Yamaya T. Geometry optimization of electrically floating PET inserts for improved RF penetration for a 3 T MRI system. Med Phys 2018; 45:4627-4641. [PMID: 30118140 DOI: 10.1002/mp.13132] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 08/08/2018] [Accepted: 08/08/2018] [Indexed: 12/30/2022] Open
Abstract
PURPOSE An electrically floating radio frequency (RF) shielded PET insert with individual PET detectors shielded by separate Faraday cages enables the MRI built-in body RF coil to be used at least as an RF transmitter, in which the RF field penetrates the imaging region inside the PET ring through the narrow gaps between the shielded PET detector modules. Because the shielded PET ring blocks more than 90% of the imaging region for the transmit field from the body RF coil, it is very challenging to obtain the required RF field inside a full-ring floating PET insert. In this study, experiments were performed on the dependence of RF penetrability on different geometric aspects of the shielded PET modules and PET rings to optimize the design parameters to obtain the required RF field inside the PET ring. METHODS We developed several prototype cylindrical full-ring PET inserts using completely enclosed empty RF shield boxes (considered as dummy PET modules). Considering the RF shield box, we conducted studies for different axial lengths (240 and 120 mm) and heights (30 and 45 mm) of the shield boxes. On the other hand, considering the PET ring geometry, we also performed studies on three different categories of PET rings: a long-ring insert (longer than the MRI phantom), a short-ring insert (shorter than the MRI phantom), and a two-ring insert that combined two short-rings. In each ring category, two different inter-shield box gaps (1 and 3 mm) were considered. In the case of the two-ring insert, three different ring-gaps (5, 10, and 20 mm) were studied. In total, 21 PET inserts were studied with an inner diameter (i.d.) of 210 mm. To study the effect of ring diameter, another long-ring insert was studied for the 270 mm i.d. Experiments were conducted for the transmit RF (B1 ) fields and signal-to-noise ratios of spin-echo and gradient-echo images using a homogeneous phantom in a 700 mm bore-diameter 3 T clinical MRI system. RF pulse amplitudes generated automatically by the MRI system were recorded for comparison. RESULTS A PET insert with a 3 mm inter-box gap was found to perform the best, at a level which is acceptable for PET imaging. In the case of an insert of multiple short-rings instead of one long-ring insert, the 5 and 10 mm ring-gaps provided higher RF field penetration. Increasing the inter-box gap improved the RF field penetration, whereas a ring-gap that was too wide concentrated the field near the ring-gap region. Relatively reduced RF power was required for wider inter-box gap or ring-gap or larger shield box height. Moreover, the rectangular shield box outperformed the trapezoidal shield box. On the other hand, when we changed the inner or outer diameter of the PET ring by keeping the same transaxial width of the shield boxes, we did not see any noticeable variation. CONCLUSIONS Our study results provide comprehensive guidance on the geometrical design aspects of RF-penetrable PET inserts for efficient RF penetration inside the PET ring. By choosing proper geometric design parameters, we could get the RF field that was similar to the MRI-only case.
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Affiliation(s)
- Md Shahadat Hossain Akram
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, 263-8555, Japan
| | - Craig S Levin
- Department of Radiology, School of Medicine, Stanford University, Stanford, CA, 94305-5128, USA
| | - Takayuki Obata
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, 263-8555, Japan
| | - Genki Hirumi
- Artificial System Science, Graduate School of Engineering, Chiba University, Chiba, 263-8522, Japan
| | - Taiga Yamaya
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, 263-8555, Japan
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Kim KB, Choi Y, Jung J, Lee S, Choe HJ, Leem HT. Analog and digital signal processing method using multi-time-over-threshold and FPGA for PET. Med Phys 2018; 45:4104-4111. [PMID: 30043982 DOI: 10.1002/mp.13101] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 07/13/2018] [Accepted: 07/13/2018] [Indexed: 11/12/2022] Open
Abstract
PURPOSE The goal of this study was to develop an analog and digital signal processing method using multi-time-over-threshold (MTOT) and field programmable gate arrays (FPGAs) to extract PET event information by using the internal clock of FPGA (~350 MHz), without ADC and TDC. METHODS The PET detector modules were composed of a 4 × 4 matrix of 3 × 3 × 20 mm3 LYSO and 4 × 4 SiPM array. Output charge signals of PET detector modules were amplified and fed into four comparators to generate trigger signals. The energy of the detected gamma ray was calculated by integrating the digitized pulse and the arrival time was determined from the time stamp of the lowest trigger signal by FPGA. The data packet containing energy, time, and position information was stored in list mode on the host computer. RESULTS The performance of analog and digital signal processing circuits using MTOT method and FPGA was evaluated by measuring energy and time resolution of the proposed method and the values were 19% and 900 ps, respectively. CONCLUSION This study demonstrated that the proposed MTOT method consisting of only FPGA without ADC and TDC could provide a simple and cost-effective analog and digital signal processing system for PET.
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Affiliation(s)
- Kyu Bom Kim
- Department of Electronic Engineering, Sogang University, 1 Shinsu-Dong, Mapo-Gu, Seoul, 121-742, South Korea
| | - Yong Choi
- Department of Electronic Engineering, Sogang University, 1 Shinsu-Dong, Mapo-Gu, Seoul, 121-742, South Korea
| | - Jiwoong Jung
- Department of Electronic Engineering, Sogang University, 1 Shinsu-Dong, Mapo-Gu, Seoul, 121-742, South Korea
| | - Sangwon Lee
- Department of Electronic Engineering, Sogang University, 1 Shinsu-Dong, Mapo-Gu, Seoul, 121-742, South Korea
| | - Hyeok-Jun Choe
- Department of Electronic Engineering, Sogang University, 1 Shinsu-Dong, Mapo-Gu, Seoul, 121-742, South Korea
| | - Hyun Tae Leem
- Department of Electronic Engineering, Sogang University, 1 Shinsu-Dong, Mapo-Gu, Seoul, 121-742, South Korea
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Chang CM, Lee BJ, Grant AM, Groll AN, Levin CS. Performance study of a radio-frequency field-penetrable PET insert for simultaneous PET/MRI. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2018; 2:422-431. [PMID: 30911706 DOI: 10.1109/trpms.2018.2852686] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Hybrid positron emission tomography (PET)/magnetic resonance imaging (MRI) has risen to the cutting edge of medical imaging technology as it allows simultaneous acquisition of structural, functional and molecular information of the patient. A PET insert that can be installed into existing MR systems can in principle reduce the cost barriers for an existing MR site to achieve simultaneous PET/MRI compared to procuring an integrated PET+MRI system. The PET insert systems developed so far for PET/MRI require the RF transmitter coil to reside inside the PET ring as those PET inserts block the RF fields from the MRI system. Here we report for the first time on the performance of a full-ring brain-sized "RF-penetrable" PET insert we have recently completed. This insert allows the RF fields generated by the built-in body coil to penetrate the PET ring. The PET insert comprises a ring of 16 detector modules employing electro-optical coupled signal transmission and a multiplexing framework based on compressed sensing. Energy resolution, coincidence timing resolution (CTR), photopeak position, and coincidence count rate were acquired outside and inside a 3-Tesla MRI system under simultaneous acquisition to evaluate the impact of MRI on the PET performance. Coincidence count rate performance was evaluated by acquiring a cylinder source with high initial activity decaying over time. Tomographic imaging of two phantoms, a custom 6.5-cm diameter resolution phantom with hot rods of four different sizes (2.8 mm, 3.2 mm, 4.2 mm, and 5.2 mm diameter) and a 3D Hoffman brain phantom, were performed to evaluate the imaging capability of the PET insert. The energy resolution at 511 keV and CTR acquired by the PET insert were 16.2±0.1% and 5.3±0.1 ns FWHM, respectively, and remained stable during MRI operation except when the EPI sequence was applied. The PET system starts to show saturation in coincidence count rate at 2.76 million photon counts per second. Most of the 2.8-mm diameter hot rods and main features of the 3D Hoffman brain phantom were resolved by the PET insert, demonstrating its high spatial resolution and capability to image a complex tracer distribution mimicking that seen in the human brain.
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Affiliation(s)
- Chen-Ming Chang
- Departments of Applied Physics and Radiology, Stanford University, Stanford, CA, USA
| | - Brian J Lee
- Departments of Mechanical Engineering and Radiology, Stanford University, Stanford, CA, USA
| | - Alexander M Grant
- Departments of Bioengineering and Radiology, Stanford University, Stanford, CA, USA
| | - Andrew N Groll
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Craig S Levin
- Departments of Radiology, Electrical Engineering, Bioengineering and Physics, Stanford University, Stanford, CA, USA, )
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Musafargani S, Ghosh KK, Mishra S, Mahalakshmi P, Padmanabhan P, Gulyás B. PET/MRI: a frontier in era of complementary hybrid imaging. Eur J Hybrid Imaging 2018; 2:12. [PMID: 29998214 PMCID: PMC6015803 DOI: 10.1186/s41824-018-0030-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Accepted: 03/14/2018] [Indexed: 12/19/2022] Open
Abstract
With primitive approaches, the diagnosis and therapy were operated at the cellular, molecular, or even at the genetic level. As the diagnostic techniques are more concentrated towards molecular level, multi modal imaging becomes specifically essential. Multi-modal imaging has extensive applications in clinical as well as in pre-clinical studies. Positron Emission Tomography (PET) has flourished in the field of nuclear medicine, which has motivated it to fuse with Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) for PET/CT and PET/MRI respectively. However, the challenges in PET/CT are due to the inability of simultaneous acquisition and reduced soft tissue contrast, which has led to the development of PET/MRI. Also, MRI offers the better soft tissue contrast over CT. Hence, fusion of PET and MRI results in combining structural information with functional image from PET. Yet, it has many technical challenges due to the interference between the modalities. Also, it must be resolved with various approaches for addressing the shortcomings of each system and improvise on the image quantification system. This review elaborates on the various challenges in the present PET/MRI system and the future directions of the hybrid modality. Also, the different data acquisition and analysis techniques of PET/MRI system are discussed with enhanced details on the software tools.
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Affiliation(s)
- Sikkandhar Musafargani
- Lee Kong Chian School of Medicine, Nanyang Technological University, 59 Nanyang Drive, Singapore, 636921 Singapore
| | - Krishna Kanta Ghosh
- Lee Kong Chian School of Medicine, Nanyang Technological University, 59 Nanyang Drive, Singapore, 636921 Singapore
| | - Sachin Mishra
- Lee Kong Chian School of Medicine, Nanyang Technological University, 59 Nanyang Drive, Singapore, 636921 Singapore
| | | | - Parasuraman Padmanabhan
- Lee Kong Chian School of Medicine, Nanyang Technological University, 59 Nanyang Drive, Singapore, 636921 Singapore
| | - Balázs Gulyás
- Lee Kong Chian School of Medicine, Nanyang Technological University, 59 Nanyang Drive, Singapore, 636921 Singapore
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Omidvari N, Topping G, Cabello J, Paul S, Schwaiger M, Ziegler SI. MR-compatibility assessment of MADPET4: a study of interferences between an SiPM-based PET insert and a 7 T MRI system. Phys Med Biol 2018; 63:095002. [PMID: 29582780 DOI: 10.1088/1361-6560/aab9d1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Compromises in the design of a positron emission tomography (PET) insert for a magnetic resonance imaging (MRI) system should minimize the deterioration of image quality in both modalities, particularly when simultaneous demanding acquisitions are performed. In this work, the advantages of using individually read-out crystals with high-gain silicon photomultipliers (SiPMs) were studied with a small animal PET insert for a 7 T MRI system, in which the SiPM charge was transferred to outside the MRI scanner using coaxial cables. The interferences between the two systems were studied with three radio-frequency (RF) coil configurations. The effects of PET on the static magnetic field, flip angle distribution, RF noise, and image quality of various MRI sequences (gradient echo, spin echo, and echo planar imaging (EPI) at 1H frequency, and chemical shift imaging at 13C frequency) were investigated. The effects of fast-switching gradient fields and RF pulses on PET count rate were studied, while the PET insert and the readout electronics were not shielded. Operating the insert inside a 1H volume coil, used for RF transmission and reception, limited the MRI to T1-weighted imaging, due to coil detuning and RF attenuation, and resulted in significant PET count loss. Using a surface receive coil allowed all tested MR sequences to be used with the insert, with 45-59% signal-to-noise ratio (SNR) degradation, compared to without PET. With a 1H/13C volume coil inside the insert and shielded by a copper tube, the SNR degradation was limited to 23-30% with all tested sequences. The insert did not introduce any discernible distortions into images of two tested EPI sequences. Use of truncated sinc shaped RF excitation pulses and gradient field switching had negligible effects on PET count rate. However, PET count rate was substantially affected by high-power RF block pulses and temperature variations due to high gradient duty cycles.
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Affiliation(s)
- Negar Omidvari
- Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675 Munich, Germany. These authors contributed equally to this work. Author to whom any correspondence should be addressed
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Jeong M, Van B, Wells BT, D'Aries LJ, Hammig MD. Scalable gamma-ray camera for wide-area search based on silicon photomultipliers array. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:033106. [PMID: 29604781 DOI: 10.1063/1.5016563] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Portable coded-aperture imaging systems based on scintillators and semiconductors have found use in a variety of radiological applications. For stand-off detection of weakly emitting materials, large volume detectors can facilitate the rapid localization of emitting materials. We describe a scalable coded-aperture imaging system based on 5.02 × 5.02 cm2 CsI(Tl) scintillator modules, each partitioned into 4 × 4 × 20 mm3 pixels that are optically coupled to 12 × 12 pixel silicon photo-multiplier (SiPM) arrays. The 144 pixels per module are read-out with a resistor-based charge-division circuit that reduces the readout outputs from 144 to four signals per module, from which the interaction position and total deposited energy can be extracted. All 144 CsI(Tl) pixels are readily distinguishable with an average energy resolution, at 662 keV, of 13.7% FWHM, a peak-to-valley ratio of 8.2, and a peak-to-Compton ratio of 2.9. The detector module is composed of a SiPM array coupled with a 2 cm thick scintillator and modified uniformly redundant array mask. For the image reconstruction, cross correlation and maximum likelihood expectation maximization methods are used. The system shows a field of view of 45° and an angular resolution of 4.7° FWHM.
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Affiliation(s)
- Manhee Jeong
- Nuclear Engineering and Radiological Sciences Department, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Benjamin Van
- Galt Research LLC, Ypsilanti, Michigan 48198, USA
| | | | - Lawrence J D'Aries
- US Army Armament Research, Development and Engineering Center (ARDEC), Picatinny Arsenal, New Jersey 07806, USA
| | - Mark D Hammig
- Nuclear Engineering and Radiological Sciences Department, University of Michigan, Ann Arbor, Michigan 48109, USA
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Akram MSH, Obata T, Suga M, Nishikido F, Yoshida E, Saito K, Yamaya T. MRI compatibility study of an integrated PET/RF-coil prototype system at 3T. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 283:62-70. [PMID: 28881235 DOI: 10.1016/j.jmr.2017.08.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 08/22/2017] [Accepted: 08/23/2017] [Indexed: 06/07/2023]
Abstract
We have been working on the development of a PET insert for existing magnetic resonance imaging (MRI) systems for simultaneous PET/MR imaging, which integrates radiofrequency (RF)-shielded PET detector modules with an RF head coil. In order to avoid interferences between the PET detector circuits and the different MRI-generated electromagnetic fields, PET detector circuits were installed inside eight Cu-shielded fiber-reinforced plastic boxes, and these eight shielded PET modules were integrated in between the eight elements of a 270-mm-diameter and 280-mm-axial-length cylindrical birdcage RF coil, which was designed to be used with a 3-T clinical MRI system. The diameter of the PET scintillators with a 12-mm axial field-of-view became 255mm, which was very close to the imaging region. In this study, we have investigated the effects of this PET/RF-coil integrated system on the performance of MRI, which include the evaluation of static field (Bo) inhomogeneity, RF field (B1) distribution, local specific absorption rate (SAR) distribution, average SAR, and signal-to-noise ratio (SNR). For the central 170-mm-diameter and 80-mm-axial-length of a homogenous cylindrical phantom (with the total diameter of 200mm and axial-length of 100mm), an increase of about a maximum of 3μT in the Bo inhomogeneity was found, both in the central and 40-mm off-centered transverse planes, and a 5 percentage point increase of B1 field inhomogeneity was observed in the central transverse plane (from 84% without PET to 79% with PET), while B1 homogeneity along the coronal plane was almost unchanged (77%) following the integration of PET with the RF head coil. The average SAR and maximum local SAR were increased by 1.21 and 1.62 times, respectively. However, the SNR study for both spin-echo and gradient-echo sequences showed a reduction of about 70% and 60%, respectively, because of the shielded PET modules. The overall results prove the feasibility of this integrated PET/RF-coil system for using with the existing MRI system.
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Affiliation(s)
- Md Shahadat Hossain Akram
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan.
| | - Takayuki Obata
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan
| | - Mikio Suga
- Center for Frontier Medical Engineering, Chiba University, Japan
| | - Fumihiko Nishikido
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan
| | - Eiji Yoshida
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan
| | - Kazuyuki Saito
- Center for Frontier Medical Engineering, Chiba University, Japan
| | - Taiga Yamaya
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan.
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Parl C, Kolb A, Schmid AM, Wehrl HF, Disselhorst JA, Soubiran PD, Stricker-Shaver D, Pichler BJ. A novel optically transparent RF shielding for fully integrated PET/MRI systems. ACTA ACUST UNITED AC 2017; 62:7357-7378. [DOI: 10.1088/1361-6560/aa8384] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Grant AM, Lee BJ, Chang CM, Levin CS. Simultaneous PET/MR imaging with a radio frequency-penetrable PET insert. Med Phys 2017; 44:112-120. [PMID: 28102949 DOI: 10.1002/mp.12031] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Revised: 09/06/2016] [Accepted: 11/22/2016] [Indexed: 11/10/2022] Open
Abstract
PURPOSE A brain sized radio frequency (RF)-penetrable PET insert has been designed for simultaneous operation with MRI systems. This system takes advantage of electro-optical coupling and battery power to electrically float the PET insert relative to the MRI ground, permitting RF signals to be transmitted through small gaps between the modules that form the PET ring. This design facilitates the use of the built-in body coil for RF transmission and thus could be inserted into any existing MR site wishing to achieve simultaneous PET/MR imaging. The PET detectors employ nonmagnetic silicon photomultipliers in conjunction with a compressed sensing signal multiplexing scheme, and optical fibers to transmit analog PET detector signals out of the MRI room for decoding, processing, and image reconstruction. METHODS The PET insert was first constructed and tested in a laboratory benchtop setting, where tomographic images of a custom resolution phantom were successfully acquired. The PET insert was then placed within a 3T body MRI system, and tomographic resolution/contrast phantom images were acquired both with only the B0 field present, and under continuous pulsing from different MR imaging sequences. RESULTS The resulting PET images have comparable contrast-to-noise ratios (CNR) under all MR pulsing conditions: The maximum percent CNR relative difference for each rod type among all four PET images acquired in the MRI system has a mean of 14.0 ± 7.7%. MR images were successfully acquired through the RF-penetrable PET shielding using only the built-in MR body coil, suggesting that simultaneous imaging is possible without significant mutual interference. CONCLUSIONS These results show promise for this technology as an alternative to costly integrated PET/MR scanners; a PET insert that is compatible with any existing clinical MRI system could greatly increase the availability, accessibility, and dissemination of PET/MR.
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Affiliation(s)
- Alexander M Grant
- Stanford University, Departments of Bioengineering, Stanford, CA, USA.,Stanford University, Departments of Radiology, Stanford, CA, USA
| | - Brian J Lee
- Stanford University, Departments of Radiology, Stanford, CA, USA.,Stanford University, Departments of Mechanical Engineering, Stanford, CA, USA
| | - Chen-Ming Chang
- Stanford University, Departments of Radiology, Stanford, CA, USA.,Stanford University, Departments of Applied Physics, Stanford, CA, USA
| | - Craig S Levin
- Stanford University, Departments of Bioengineering, Stanford, CA, USA.,Stanford University, Departments of Radiology, Stanford, CA, USA.,Stanford University, Departments of Electrical Engineering, Stanford, CA, USA.,Stanford University, Departments of Physics, Stanford, CA, USA
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Thiessen JD, Shams E, Stortz G, Schellenberg G, Bishop D, Khan MS, Kozlowski P, Retière F, Sossi V, Thompson CJ, Goertzen AL. MR-compatibility of a high-resolution small animal PET insert operating inside a 7 T MRI. Phys Med Biol 2016; 61:7934-7956. [DOI: 10.1088/0031-9155/61/22/7934] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Hirano Y, Nishikido F, Kokuryo D, Yamaya T. After-pulsing, cross-talk, dark-count, and gain of MPPC under 7-T static magnetic field. Radiol Phys Technol 2016; 9:245-53. [PMID: 27188511 DOI: 10.1007/s12194-016-0356-3] [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: 03/14/2016] [Revised: 04/28/2016] [Accepted: 05/04/2016] [Indexed: 11/28/2022]
Abstract
Multi-pixel photon counters (MPPCs) have been used instead of photomultiplier tubes for positron emission tomography combined with magnetic resonance (PET-MR). However, the effects of the magnetic field (MF) on the intrinsic properties-gain, cross-talk, after-pulsing, and dark-count-have not been sufficiently investigated. Therefore, we measured these properties for two types of MPPCs-S10931-50P and S12572-50P-in a static 7-T MF. These properties were measured with a pulse-shape analysis using pulse data acquired by a digital oscilloscope in the presence of the MF (w/MF) and the absence of the MF (w/o MF) by changing the supplied over-voltages (from 0.95 to 2.1 V for S10931 and from 2.1 to 3.3 V for S12572). No significant differences between the w/MF and w/o MF cases were observed for either MPPC, suggesting that the gain, cross-talk, after-pulsing, and dark-count are insensitive to a 7-T MF. The present work shows that constant MPPC performance is expected under a strong MF and demonstrates positive results for PET-MR.
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Affiliation(s)
- Yoshiyuki Hirano
- Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan. .,Gunma University, 3-39-22 Showa-Machi, Maebashi, Gunma, 371-8511, Japan.
| | - Fumihiko Nishikido
- Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Daisuke Kokuryo
- Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Taiga Yamaya
- Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
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Gebhardt P, Wehner J, Weissler B, Botnar R, Marsden PK, Schulz V. FPGA-based RF interference reduction techniques for simultaneous PET-MRI. Phys Med Biol 2016; 61:3500-26. [PMID: 27049898 PMCID: PMC5362065 DOI: 10.1088/0031-9155/61/9/3500] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2015] [Revised: 11/13/2015] [Accepted: 01/28/2016] [Indexed: 11/30/2022]
Abstract
The combination of positron emission tomography (PET) and magnetic resonance imaging (MRI) as a multi-modal imaging technique is considered very promising and powerful with regard to in vivo disease progression examination, therapy response monitoring and drug development. However, PET-MRI system design enabling simultaneous operation with unaffected intrinsic performance of both modalities is challenging. As one of the major issues, both the PET detectors and the MRI radio-frequency (RF) subsystem are exposed to electromagnetic (EM) interference, which may lead to PET and MRI signal-to-noise ratio (SNR) deteriorations. Early digitization of electronic PET signals within the MRI bore helps to preserve PET SNR, but occurs at the expense of increased amount of PET electronics inside the MRI and associated RF field emissions. This raises the likelihood of PET-related MRI interference by coupling into the MRI RF coil unwanted spurious signals considered as RF noise, as it degrades MRI SNR and results in MR image artefacts. RF shielding of PET detectors is a commonly used technique to reduce PET-related RF interferences, but can introduce eddy-current-related MRI disturbances and hinder the highest system integration. In this paper, we present RF interference reduction methods which rely on EM field coupling-decoupling principles of RF receive coils rather than suppressing emitted fields. By modifying clock frequencies and changing clock phase relations of digital circuits, the resulting RF field emission is optimised with regard to a lower field coupling into the MRI RF coil, thereby increasing the RF silence of PET detectors. Our methods are demonstrated by performing FPGA-based clock frequency and phase shifting of digital silicon photo-multipliers (dSiPMs) used in the PET modules of our MR-compatible Hyperion II (D) PET insert. We present simulations and magnetic-field map scans visualising the impact of altered clock phase pattern on the spatial RF field distribution, followed by MRI noise and SNR scans performed with an operating PET module using different clock frequencies and phase patterns. The methods were implemented via firmware design changes without any hardware modifications. This introduces new means of flexibility by enabling adaptive RF interference reduction optimisations in the field, e.g. when using a PET insert with different MRI systems or when different MRI RF coil types are to be operated with the same PET detector.
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Affiliation(s)
- P Gebhardt
- Division of Imaging Sciences and Biomedical Engineering, King’s College London, London WC2R 2LS, UK
- Department of Physics of Molecular Imaging Systems, Institute of Experimental Molecular Imaging, RWTH Aachen University, 52062 Aachen, Germany
| | - J Wehner
- Department of Physics of Molecular Imaging Systems, Institute of Experimental Molecular Imaging, RWTH Aachen University, 52062 Aachen, Germany
| | - B Weissler
- Department of Physics of Molecular Imaging Systems, Institute of Experimental Molecular Imaging, RWTH Aachen University, 52062 Aachen, Germany
| | - R Botnar
- Division of Imaging Sciences and Biomedical Engineering, King’s College London, London WC2R 2LS, UK
| | - P K Marsden
- Division of Imaging Sciences and Biomedical Engineering, King’s College London, London WC2R 2LS, UK
| | - V Schulz
- Department of Physics of Molecular Imaging Systems, Institute of Experimental Molecular Imaging, RWTH Aachen University, 52062 Aachen, Germany
- Philips Research Europe, 52066 Aachen, Germany
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Jung JH, Choi Y, Jung J, Kim S, Lim HK, Im KC, Oh CH, Park HW, Kim KM, Kim JG. Development of PET/MRI with insertable PET for simultaneous PET and MR imaging of human brain. Med Phys 2016; 42:2354-63. [PMID: 25979030 DOI: 10.1118/1.4918321] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The purpose of this study was to develop a dual-modality positron emission tomography (PET)/magnetic resonance imaging (MRI) with insertable PET for simultaneous PET and MR imaging of the human brain. METHODS The PET detector block was composed of a 4 × 4 matrix of detector modules, each consisting of a 4 × 4 array LYSO coupled to a 4 × 4 Geiger-mode avalanche photodiode (GAPD) array. The PET insert consisted of 18 detector blocks, circularly mounted on a custom-made plastic base to form a ring with an inner diameter of 390 mm and axial length of 60 mm. The PET gantry was shielded with gold-plated conductive fabric tapes with a thickness of 0.1 mm. The charge signals of PET detector transferred via 4 m long flat cables were fed into the position decoder circuit. The flat cables were shielded with a mesh-type aluminum sheet with a thickness of 0.24 mm. The position decoder circuit and field programmable gate array-embedded DAQ modules were enclosed in an aluminum box with a thickness of 10 mm and located at the rear of the MR bore inside the MRI room. A 3-T human MRI system with a Larmor frequency of 123.7 MHz and inner bore diameter of 60 cm was used as the PET/MRI hybrid system. A custom-made radio frequency (RF) coil with an inner diameter of 25 cm was fabricated. The PET was positioned between gradient and the RF coils. PET performance was measured outside and inside the MRI scanner using echo planar imaging, spin echo, turbo spin echo, and gradient echo sequences. MRI performance was also evaluated with and without the PET insert. The stability of the newly developed PET insert was evaluated and simultaneous PET and MR images of a brain phantom were acquired. RESULTS No significant degradation of the PET performance caused by MR was observed when the PET was operated using various MR imaging sequences. The signal-to-noise ratio of MR images was slightly degraded due to the PET insert installed inside the MR bore while the homogeneity was maintained. The change of gain of the 256 GAPD/scintillator elements of a detector block was <3% for 60 min, and simultaneous PET and MR images of a brain phantom were successfully acquired. CONCLUSIONS Experimental results indicate that a compact and lightweight PET insert for hybrid PET/MRI can be developed using GAPD arrays and charge signal transmission method proposed in this study without significant interference.
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Affiliation(s)
- Jin Ho Jung
- Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 121-742, Korea
| | - Yong Choi
- Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 121-742, Korea
| | - Jiwoong Jung
- Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 121-742, Korea
| | - Sangsu Kim
- Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 121-742, Korea
| | - Hyun Keong Lim
- Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 121-742, Korea
| | - Ki Chun Im
- Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 121-742, Korea
| | - Chang Hyun Oh
- Department of Electrical Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea
| | - Hyun-wook Park
- Department of Electrical Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea
| | - Kyung Min Kim
- Korea Institute of Radiological and Medical Science, 75 Nowon-ro, Nowon-gu, Seoul 139-709, Korea
| | - Jong Guk Kim
- Korea Institute of Radiological and Medical Science, 75 Nowon-ro, Nowon-gu, Seoul 139-709, Korea
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Ullah MN, Pratiwi E, Cheon J, Choi H, Yeom JY. Instrumentation for Time-of-Flight Positron Emission Tomography. Nucl Med Mol Imaging 2016; 50:112-22. [PMID: 27275359 DOI: 10.1007/s13139-016-0401-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 12/08/2015] [Accepted: 01/25/2016] [Indexed: 10/22/2022] Open
Abstract
Positron emission tomography (PET) is a molecular imaging modality that provides information at the molecular level. This system is composed of radiation detectors to detect incoming coincident annihilation gamma photons emitted from the radiopharmaceutical injected into a patient's body and uses these data to reconstruct images. A major trend in PET instrumentation is the development of time-of-flight positron emission tomography (ToF-PET). In ToF-PET, the time information (the instant the radiation is detected) is incorporated for image reconstruction. Therefore, precise and accurate timing recording is crucial in ToF-PET. ToF-PET leads to better localization of the annihilation event and thus results in overall improvement in the signal-to-noise ratio (SNR) of the reconstructed image. Several factors affect the timing performance of ToF-PET. In this article, the background, early research and recent advances in ToF-PET instrumentation are presented. Emphasis is placed on the various types of scintillators, photodetectors and electronic circuitry for use in ToF-PET, and their impact on timing resolution is discussed.
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Affiliation(s)
- Muhammad Nasir Ullah
- Graduate School of Bio-Convergence Engineering, College of Health Sciences, Korea University, Seoul, South Korea
| | - Eva Pratiwi
- Graduate School of Bio-Convergence Engineering, College of Health Sciences, Korea University, Seoul, South Korea
| | - Jimin Cheon
- School of Electronic Engineering, Kumoh National Institute of Technology, Gumi, South Korea
| | - Hojong Choi
- Department of Medical IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, South Korea
| | - Jung Yeol Yeom
- Graduate School of Bio-Convergence Engineering, College of Health Sciences, Korea University, Seoul, South Korea ; Department of Biomedical Engineering, Korea University, Seoul, South Korea
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Goldschmidt B, Schug D, Lerche CW, Salomon A, Gebhardt P, Weissler B, Wehner J, Dueppenbecker PM, Kiessling F, Schulz V. Software-Based Real-Time Acquisition and Processing of PET Detector Raw Data. IEEE Trans Biomed Eng 2016; 63:316-27. [DOI: 10.1109/tbme.2015.2456640] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
Multimodal imaging has led to a more detailed exploration of different physiologic processes with integrated PET/MR imaging being the most recent entry. Although the clinical need is still questioned, it is well recognized that it represents one of the most active and promising fields of medical imaging research in terms of software and hardware. The hardware developments have moved from small detector components to high-performance PET inserts and new concepts in full systems. Conversely, the software focuses on the efficient performance of necessary corrections without the use of CT data. The most recent developments in both directions are reviewed.
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Affiliation(s)
- Charalampos Tsoumpas
- Division of Biomedical Imaging, Faculty of Medicine and Health, University of Leeds, 8.001a, Worsley Building, Clarendon Way, Leeds LS2 9JT, UK
| | - Dimitris Visvikis
- LaTIM UMR 1101, INSERM, University of Brest, Bat 1, 1er etage, 5 avenue Foch, Brest 29609, France
| | - George Loudos
- Department of Biomedical Engineering, Technological Educational Institute of Athens, Ag. Spiridonos 28, Egaleo, Athens 12210, Greece.
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Jung JH, Choi Y, Im KC. PET/MRI: Technical Challenges and Recent Advances. Nucl Med Mol Imaging 2016; 50:3-12. [PMID: 26941854 DOI: 10.1007/s13139-016-0393-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 12/17/2015] [Accepted: 01/06/2016] [Indexed: 11/28/2022] Open
Abstract
Integrated positron emission tomography (PET)/magnetic resonance imaging (MRI), which can provide complementary functional and anatomical information about a specific organ or body system at the molecular level, has become a powerful imaging modality to understand the molecular biology details, disease mechanisms, and pharmacokinetics in animals and humans. Although the first experiment on the PET/MRI was performed in the early 1990s, its clinical application was accomplished in recent years because there were various technical challenges in integrating PET and MRI in a single system with minimum mutual interference between PET and MRI. This paper presents the technical challenges and recent advances in combining PET and MRI along with several approaches for improving PET image quality of the PET/MRI hybrid imaging system.
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Affiliation(s)
- Jin Ho Jung
- Molecular Imaging Research & Education Laboratory, Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107 Korea
| | - Yong Choi
- Molecular Imaging Research & Education Laboratory, Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107 Korea
| | - Ki Chun Im
- Molecular Imaging Research & Education Laboratory, Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107 Korea
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Weissler B, Gebhardt P, Dueppenbecker PM, Wehner J, Schug D, Lerche CW, Goldschmidt B, Salomon A, Verel I, Heijman E, Perkuhn M, Heberling D, Botnar RM, Kiessling F, Schulz V. A Digital Preclinical PET/MRI Insert and Initial Results. IEEE TRANSACTIONS ON MEDICAL IMAGING 2015; 34:2258-2270. [PMID: 25935031 DOI: 10.1109/tmi.2015.2427993] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Combining Positron Emission Tomography (PET) with Magnetic Resonance Imaging (MRI) results in a promising hybrid molecular imaging modality as it unifies the high sensitivity of PET for molecular and cellular processes with the functional and anatomical information from MRI. Digital Silicon Photomultipliers (dSiPMs) are the digital evolution in scintillation light detector technology and promise high PET SNR. DSiPMs from Philips Digital Photon Counting (PDPC) were used to develop a preclinical PET/RF gantry with 1-mm scintillation crystal pitch as an insert for clinical MRI scanners. With three exchangeable RF coils, the hybrid field of view has a maximum size of 160 mm × 96.6 mm (transaxial × axial). 0.1 ppm volume-root-mean-square B 0-homogeneity is kept within a spherical diameter of 96 mm (automatic volume shimming). Depending on the coil, MRI SNR is decreased by 13% or 5% by the PET system. PET count rates, energy resolution of 12.6% FWHM, and spatial resolution of 0.73 mm (3) (isometric volume resolution at isocenter) are not affected by applied MRI sequences. PET time resolution of 565 ps (FWHM) degraded by 6 ps during an EPI sequence. Timing-optimized settings yielded 260 ps time resolution. PET and MR images of a hot-rod phantom show no visible differences when the other modality was in operation and both resolve 0.8-mm rods. Versatility of the insert is shown by successfully combining multi-nuclei MRI ((1)H/(19)F) with simultaneously measured PET ((18)F-FDG). A longitudinal study of a tumor-bearing mouse verifies the operability, stability, and in vivo capabilities of the system. Cardiac- and respiratory-gated PET/MRI motion-capturing (CINE) images of the mouse heart demonstrate the advantage of simultaneous acquisition for temporal and spatial image registration.
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Du J, Schmall JP, Yang Y, Di K, Roncali E, Mitchell GS, Buckley S, Jackson C, Cherry SR. Evaluation of Matrix9 silicon photomultiplier array for small-animal PET. Med Phys 2015; 42:585. [PMID: 25652479 DOI: 10.1118/1.4905088] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The MatrixSL-9-30035-OEM (Matrix9) from SensL is a large-area silicon photomultiplier (SiPM) photodetector module consisting of a 3 × 3 array of 4 × 4 element SiPM arrays (total of 144 SiPM pixels) and incorporates SensL's front-end electronics board and coincidence board. Each SiPM pixel measures 3.16 × 3.16 mm(2) and the total size of the detector head is 47.8 × 46.3 mm(2). Using 8 × 8 polished LSO/LYSO arrays (pitch 1.5 mm) the performance of this detector system (SiPM array and readout electronics) was evaluated with a view for its eventual use in small-animal positron emission tomography (PET). METHODS Measurements of noise, signal, signal-to-noise ratio, energy resolution, flood histogram quality, timing resolution, and array trigger error were obtained at different bias voltages (28.0-32.5 V in 0.5 V intervals) and at different temperatures (5 °C-25 °C in 5 °C degree steps) to find the optimal operating conditions. RESULTS The best measured signal-to-noise ratio and flood histogram quality for 511 keV gamma photons were obtained at a bias voltage of 30.0 V and a temperature of 5 °C. The energy resolution and timing resolution under these conditions were 14.2% ± 0.1% and 4.2 ± 0.1 ns, respectively. The flood histograms show that all the crystals in the 1.5 mm pitch LSO array can be clearly identified and that smaller crystal pitches can also be resolved. Flood histogram quality was also calculated using different center of gravity based positioning algorithms. Improved and more robust results were achieved using the local 9 pixels for positioning along with an energy offset calibration. To evaluate the front-end detector readout, and multiplexing efficiency, an array trigger error metric is introduced and measured at different lower energy thresholds. Using a lower energy threshold greater than 150 keV effectively eliminates any mispositioning between SiPM arrays. CONCLUSIONS In summary, the Matrix9 detector system can resolve high-resolution scintillator arrays common in small-animal PET with adequate energy resolution and timing resolution over a large detector area. The modular design of the Matrix9 detector allows it to be used as a building block for simple, low channel-count, yet high performance, small animal PET or PET/MRI systems.
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Affiliation(s)
- Junwei Du
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Jeffrey P Schmall
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Yongfeng Yang
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Kun Di
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Emilie Roncali
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Gregory S Mitchell
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California 95616
| | - Steve Buckley
- SensL Technologies Ltd., 6800 Airport Business Park, Cork, Ireland
| | - Carl Jackson
- SensL Technologies Ltd., 6800 Airport Business Park, Cork, Ireland
| | - Simon R Cherry
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, California, 95616
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Chang CM, Grant AM, Lee BJ, Kim E, Hong K, Levin CS. Performance characterization of compressed sensing positron emission tomography detectors and data acquisition system. Phys Med Biol 2015; 60:6407-21. [PMID: 26237671 DOI: 10.1088/0031-9155/60/16/6407] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In the field of information theory, compressed sensing (CS) had been developed to recover signals at a lower sampling rate than suggested by the Nyquist-Shannon theorem, provided the signals have a sparse representation with respect to some base. CS has recently emerged as a method to multiplex PET detector readouts thanks to the sparse nature of 511 keV photon interactions in a typical PET study. We have shown in our previous numerical studies that, at the same multiplexing ratio, CS achieves higher signal-to-noise ratio (SNR) compared to Anger and cross-strip multiplexing. In addition, unlike Anger logic, multiplexing by CS preserves the capability to resolve multi-hit events, in which multiple pixels are triggered within the resolving time of the detector. In this work, we characterized the time, energy and intrinsic spatial resolution of two CS detectors and a data acquisition system we have developed for a PET insert system for simultaneous PET/MRI. The CS detector comprises a 2 x 4 mosaic of 4 x 4 arrays of 3.2 x 3.2 x 20 mm(3) lutetium-yttrium orthosilicate crystals coupled one-to-one to eight 4 x 4 silicon photomultiplier arrays. The total number of 128 pixels is multiplexed down to 16 readout channels by CS. The energy, coincidence time and intrinsic spatial resolution achieved by two CS detectors were 15.4±0.1% FWHM at 511 keV, 4.5 ns FWHM and 2.3 mm FWHM, respectively. A series of experiments were conducted to measure the sources of time jitter that limit the time resolution of the current system, which provides guidance for potential system design improvements. These findings demonstrate the feasibility of compressed sensing as a promising multiplexing method for PET detectors.
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Affiliation(s)
- Chen-Ming Chang
- Department of Applied Physics, Stanford University, Stanford, CA 94305, USA. Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University, Stanford, CA 94305, USA
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Bieniosek MF, Levin CS. Analog electro-optical readout of SiPMs achieves fast timing required for time-of-flight PET/MR. Phys Med Biol 2015; 60:3795-806. [PMID: 25905626 DOI: 10.1088/0031-9155/60/9/3795] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The design of combined positron emission tomography/magnetic resonance (PET/MR) systems presents a number of challenges to engineers, as it forces the PET system to acquire data in a space constrained environment that is sensitive to electro-magnetic interference and contains high static, radio frequency and gradient fields. In this work we validate fast timing performance of a PET scintillation detector using a potentially very compact, very low power, and MR compatible readout method in which analog silicon photomultipliers (SiPM) signals are transmitted optically away from the MR bore with little or even no additional readout electronics. This analog 'electro-optial' method could reduce the entire PET readout in the MR bore to two compact, low power components (SiPMs and lasers). Our experiments show fast timing performance from analog electro-optical readout with and without pre-amplification. With 3 mm × 3 mm × 20 mm lutetium-yttrium oxyorthosilicate (LYSO) crystals and Excelitas SiPMs the best two-sided fwhm coincident timing resolution achieved was 220 +/- 3 ps in electrical mode, 230 +/- 2 ps in electro-optical with preamp mode, and 253 +/- 2 ps in electro-optical without preamp mode. Timing measurements were also performed with Hamamatsu SiPMs and 3 mm × 3 mm × 5 mm crystals. In the future the timing degradation seen can be further reduced with lower laser noise or improvements SiPM rise time or gain.
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Affiliation(s)
- M F Bieniosek
- Department of Radiology, Stanford University, Stanford CA 94305, USA. Molecular Imaging Program at Stanford (MIPS), Stanford CA 94305, USA. Department of Electrical Engineering, Stanford University, Stanford CA 94305, USA
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Olcott P, Kim E, Hong K, Lee BJ, Grant AM, Chang CM, Glover G, Levin CS. Prototype positron emission tomography insert with electro-optical signal transmission for simultaneous operation with MRI. Phys Med Biol 2015; 60:3459-78. [PMID: 25856511 DOI: 10.1088/0031-9155/60/9/3459] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The simultaneous acquisition of PET and MRI data shows promise to provide powerful capabilities to study disease processes in human subjects, guide the development of novel treatments, and monitor therapy response and disease progression. A brain-size PET detector ring insert for an MRI system is being developed that, if successful, can be inserted into any existing MRI system to enable simultaneous PET and MRI images of the brain to be acquired without mutual interference. The PET insert uses electro-optical coupling to relay all the signals from the PET detectors out of the MRI system using analog modulated lasers coupled to fiber optics. Because the fibers use light instead of electrical signals, the PET detector can be electrically decoupled from the MRI making it partially transmissive to the RF field of the MRI. The SiPM devices and low power lasers were powered using non-magnetic MRI compatible batteries. Also, the number of laser-fiber channels in the system was reduced using techniques adapted from the field of compressed sensing. Using the fact that incoming PET data is sparse in time and space, electronic circuits implementing constant weight codes uniquely encode the detector signals in order to reduce the number of electro-optical readout channels by 8-fold. Two out of a total of sixteen electro-optical detector modules have been built and tested with the entire RF-shielded detector gantry for the PET ring insert. The two detectors have been tested outside and inside of a 3T MRI system to study mutual interference effects and simultaneous performance with MRI. Preliminary results show that the PET insert is feasible for high resolution simultaneous PET/MRI imaging for applications in the brain.
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Affiliation(s)
- Peter Olcott
- Stanford University School of Medicine, Department of Radiology, Molecular Imaging Instrumentation Laboratory, Alway Building, Room M001, Stanford, CA 94305-5128, USA
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Wehner J, Weissler B, Dueppenbecker PM, Gebhardt P, Goldschmidt B, Schug D, Kiessling F, Schulz V. MR-compatibility assessment of the first preclinical PET-MRI insert equipped with digital silicon photomultipliers. Phys Med Biol 2015; 60:2231-55. [PMID: 25684065 DOI: 10.1088/0031-9155/60/6/2231] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PET (positron emission tomography) with its high sensitivity in combination with MRI (magnetic resonance imaging) providing anatomic information with good soft-tissue contrast is considered to be a promising hybrid imaging modality. However, the integration of a PET detector into an MRI system is a challenging task since the MRI system is a sensitive device for external disturbances and provides a harsh environment for electronic devices. Consequently, the PET detector has to be transparent for the MRI system and insensitive to electromagnetic disturbances. Due to the variety of MRI protocols imposing a wide range of requirements regarding the MR-compatibility, an extensive study is mandatory to reliably assess worst-case interference phenomena between the PET detector and the MRI scanner. We have built the first preclinical PET insert, designed for a clinical 3 T MRI, using digital silicon photomultipliers (digital SiPM, type DPC 3200-22, Philips Digital Photon Counting). Since no thorough interference investigation with this new digital sensor has been reported so far, we present in this work such a comprehensive MR-compatibility study. Acceptable distortion of the B0 field homogeneity (volume RMS = 0.08 ppm, peak-to-peak value = 0.71 ppm) has been found for the PET detector installed. The signal-to-noise ratio degradation stays between 2-15% for activities up to 21 MBq. Ghosting artifacts were only found for demanding EPI (echo planar imaging) sequences with read-out gradients in Z direction caused by additional eddy currents originated from the PET detector. On the PET side, interference mainly between the gradient system and the PET detector occurred: extreme gradient tests were executed using synthetic sequences with triangular pulse shape and maximum slew rate. Under this condition, a relative degradation of the energy (⩽10%) and timing (⩽15%) resolution was noticed. However, barely measurable performance deterioration occurred when morphological MRI protocols are conducted certifying that the overall PET performance parameters remain unharmed.
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Affiliation(s)
- J Wehner
- Department for Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging Systems, RWTH Aachen University, Pauwelsstrasse 19, 52074 Aachen, Germany
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Vandenberghe S, Marsden PK. PET-MRI: a review of challenges and solutions in the development of integrated multimodality imaging. Phys Med Biol 2015; 60:R115-54. [PMID: 25650582 DOI: 10.1088/0031-9155/60/4/r115] [Citation(s) in RCA: 143] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The integration of positron emission tomography (PET) and magnetic resonance imaging (MRI) has been an ongoing research topic for the last 20 years. This paper gives an overview of the different developments and the technical problems associated with combining PET and MRI in one system. After explaining the different detector concepts for integrating PET-MRI and minimising interference the limitations and advantages of different solutions for the detector and system are described for preclinical and clinical imaging systems. The different integrated PET-MRI systems are described in detail. Besides detector concepts and system integration the challenges and proposed solutions for attenuation correction and the potential for motion correction and resolution recovery are also discussed in this topical review.
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Affiliation(s)
- Stefaan Vandenberghe
- Department of Electronics and Information Systems, MEDISIP, Ghent University-iMinds Medical IT-IBiTech, De Pintelaan 185 block B, B-9000 Ghent, Belgium
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Yoon DK, Jung JY, Jo Hong K, Sil Lee K, Suk Suh T. GPU-based prompt gamma ray imaging from boron neutron capture therapy. Med Phys 2015; 42:165-9. [PMID: 25563257 DOI: 10.1118/1.4903265] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The purpose of this research is to perform the fast reconstruction of a prompt gamma ray image using a graphics processing unit (GPU) computation from boron neutron capture therapy (BNCT) simulations. METHODS To evaluate the accuracy of the reconstructed image, a phantom including four boron uptake regions (BURs) was used in the simulation. After the Monte Carlo simulation of the BNCT, the modified ordered subset expectation maximization reconstruction algorithm using the GPU computation was used to reconstruct the images with fewer projections. The computation times for image reconstruction were compared between the GPU and the central processing unit (CPU). Also, the accuracy of the reconstructed image was evaluated by a receiver operating characteristic (ROC) curve analysis. RESULTS The image reconstruction time using the GPU was 196 times faster than the conventional reconstruction time using the CPU. For the four BURs, the area under curve values from the ROC curve were 0.6726 (A-region), 0.6890 (B-region), 0.7384 (C-region), and 0.8009 (D-region). CONCLUSIONS The tomographic image using the prompt gamma ray event from the BNCT simulation was acquired using the GPU computation in order to perform a fast reconstruction during treatment. The authors verified the feasibility of the prompt gamma ray image reconstruction using the GPU computation for BNCT simulations.
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Affiliation(s)
- Do-Kun Yoon
- Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 505 137-701, Korea
| | - Joo-Young Jung
- Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 505 137-701, Korea
| | - Key Jo Hong
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University, 300 Pasteur Drive, Stanford, California 94305
| | - Keum Sil Lee
- Department of Radiation Oncology, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, California 94305-5847
| | - Tae Suk Suh
- Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 505 137-701, Korea
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Kim H, Sul WS, Cho G. Characterization of silicon photomultipliers at National Nano-Fab Center for PET-MR. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:103107. [PMID: 25362371 DOI: 10.1063/1.4896757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The silicon photomultipliers (SiPMs) were fabricated for magnetic resonance compatible positron emission tomography (PET) applications using customized CMOS processes at National NanoFab Center. Each micro-cell consists of a shallow n+/p well junction on a p-type epitaxial wafer and passive quenching circuit was applied. The size of the SiPM is 3 × 3 mm(2) and the pitch of each micro-cell is 65 μm. In this work, several thousands of SiPMs were packaged and tested to build a PET ring detector which has a 60 mm axial and 390 mm radial field of view. I-V characteristics of the SiPMs are shown good uniformity and breakdown voltage is around 20 V. The photon detection efficiency was measured via photon counting method and the maximum value was recorded as 16% at 470 nm. The gamma ray spectrum of a Ge-68 isotope showed nearly 10% energy resolution at 511 keV with a 3 × 3 × 20 mm(3) LYSO crystal.
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Affiliation(s)
- Hyoungtaek Kim
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, South Korea
| | - Woo Suk Sul
- National NanoFab Center, Daejeon 305-701, South Korea
| | - Gyuseong Cho
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, South Korea
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Weissler B, Gebhardt P, Lerche CW, Wehner J, Solf T, Goldschmidt B, Mackewn JE, Marsden PK, Kiessling F, Perkuhn M, Heberling D, Schulz V. MR compatibility aspects of a silicon photomultiplier-based PET/RF insert with integrated digitisation. Phys Med Biol 2014; 59:5119-39. [DOI: 10.1088/0031-9155/59/17/5119] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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