SimPET: a Preclinical PET Insert for Simultaneous PET/MR Imaging
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RESEARCH ARTICLE
SimPET: a Preclinical PET Insert for Simultaneous PET/MR Imaging Jeong-Whan Son,1 Kyeong Yun Kim,1,2,3 Ji Yong Park,2,3 Kyuwan Kim,1 Yun-Sang Lee,3 Guen Bae Ko,1,3 Jae Sung Lee1,2,3 1
Brightonix Imaging Inc., Yeonmujang 5ga-gil, Seongdong-gu, Seoul, 04782, South Korea Department of Biomedical Sciences, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea 3 Department of Nuclear Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea 2
Abstract Purpose: SimPET/M7 system is a small-animal dedicated simultaneous positron emission tomography and magnetic resonance imaging (PET/MRI) scanner. The SimPET insert has been upgraded from its prototype with a focus on count rate performance and sensitivity. The M7 scanner is a 1-T permanent magnet-based compact MRI system without any cryogens. Here, we present performance evaluation results of SimPET along with the results of mutual interference evaluation and simultaneously acquired PET/MR imaging. Procedures: Following NEMA NU 4-2008 standard, we evaluated the performance of the SimPET system. The M7 MRI compatibility of SimPET was also assessed by analyzing MRI images of a uniform phantom under different PET conditions and PET count rates with different MRI pulse sequences. Mouse imaging was performed including a whole-body 18F-NaF PET scan and a simultaneous PET/MRI scan with 64Cu-NOTA-ironoxide. Results: The spatial resolution at center based on 3D OSEM without and with warm background was 0.7 mm and 1.45 mm, respectively. Peak sensitivity was 4.21 % (energy window = 250– 750 keV). The peak noise equivalent count rate with the same energy window was 151 kcps at 38.4 MBq. The uniformity was 4.42 %, and the spillover ratios in water- and air-filled chambers were 14.6 % and 12.7 %, respectively. In the hot rod phantom image, 0.75-mm-diameter rods were distinguishable. There were no remarkable differences in the SNR and uniformity of MRI images and PET count rates with different PET conditions and MRI pulse sequences. In the whole-body 18F-NaF PET images, fine skeletal structures were well resolved. In the simultaneous PET/MRI study with 64Cu-NOTA-ironoxide, both PET and MRI signals changed before and after injection of the dual-modal imaging probe, which was evident with the exact spatiotemporal correlation. Conclusions: We demonstrated that the SimPET scanner has a high count rate performance and excellent spatial resolution. The combined SimPET/M7 enabled simultaneous PET/MR imaging studies with no remarkable mutual interference between the two imaging modalities. Key words: PET/MRI, Simultaneous imaging, NEMA performance
Jeong-Whan Son and Kyeong Yun Kim contributed equally to this work. Electronic supplementary material The online version of this article (https:// doi.org/10.1007/s11307-020-01491-y) contains supplementary material, which is available to authorized users. Correspondence to: Guen Ko; e-mail: [email protected], Jae Lee; e-mail: [email protected]
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