Kim Kyeong Yun, Son Jeong-Whan, Kim Kyuwan, Chung Yina, Park Ji Yong, Lee Yun-Sang, Ko Guen Bae, Lee Jae Sung
Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea.
Brightonix Imaging Inc., #1705, Seongsu-yeok SK V1 Tower, 25, Yeonmujang 5ga-gil, Seongdong-gu, Seoul, 04782, Korea.
Mol Imaging Biol. 2021 Oct;23(5):703-713. doi: 10.1007/s11307-021-01595-z. Epub 2021 Mar 25.
In this study, a small animal PET insert (SimPET-X, Brightonix Imaging Inc.) for simultaneous PET/MR imaging studies is presented. This insert covers an 11-cm-long axial field-of-view (FOV) and enables imaging of mouse total-bodies and rat heads.
SimPET-X comprises 16 detector modules to yield a ring diameter of 63 mm and an axial FOV of 110 mm. The detector module supports four detector blocks, each comprising two 4 × 4 SiPM arrays coupled with a 20 × 9 array of LSO crystals (1.2 × 1.2 × 10 mm). The physical characteristics of SimPET-X were measured in accordance with the NEMA NU4-2008 standard protocol. In addition, we assessed the compatibility of SimPET-X with a small animal-dedicated MRI (M7, Aspect Imaging) and conducted phantom and animal studies.
The radial spatial resolutions at the center based on 3D OSEM without and with the warm background were 0.73 mm and 0.99 mm, respectively. The absolute peak sensitivity of the system was 10.44% with an energy window of 100-900 keV and 8.27% with an energy window of 250-750 keV. The peak NECR and scatter fraction for the mouse phantom were 348 kcps at 26.2 MBq and 22.1% with an energy window of 250-750 keV, respectively. The standard deviation of pixel value in the uniform region of an NEMA IQ phantom was 4.57%. The spillover ratios for air- and water-filled chambers were 9.0% and 11.0%, respectively. In the hot-rod phantom image reconstructed using 3D OSEM-PSF, all small rods were resolved owing to the high spatial resolution of the SimPET-X system. There was no notable interference between SimPET-X and M7 MRI. SimPET-X provided high-quality mouse images with superior spatial resolution, sensitivity, and counting rate performance.
SimPET-X yielded a remarkably improved sensitivity and NECR compared with SimPET.
在本研究中，介绍了一种用于同时进行PET/MR成像研究的小动物PET插入件（SimPET-X，Brightonix Imaging Inc.）。该插入件覆盖11厘米长的轴向视野（FOV），能够对小鼠全身和大鼠头部进行成像。
SimPET-X由16个探测器模块组成，环形直径为63毫米，轴向视野为110毫米。探测器模块支持四个探测器块，每个探测器块包括两个4×4 SiPM阵列，与一个20×9的LSO晶体阵列（1.2×1.2×10毫米）耦合。根据NEMA NU4-2008标准协议测量了SimPET-X的物理特性。此外，我们评估了SimPET-X与小动物专用MRI（M7，Aspect Imaging）的兼容性，并进行了体模和动物研究。
基于3D OSEM且无热本底和有热本底时，中心处的径向空间分辨率分别为0.73毫米和0.99毫米。系统的绝对峰值灵敏度在能量窗为100 - 900 keV时为10.44%，在能量窗为250 - 750 keV时为8.27%。小鼠体模的峰值NECR和散射分数在能量窗为250 - 750 keV时，分别为26.2 MBq下的348 kcps和22.1%。NEMA IQ体模均匀区域像素值的标准偏差为4.57%。空气腔和水腔的溢出率分别为9.0%和11.0%。在使用3D OSEM-PSF重建的热棒体模图像中，由于SimPET-X系统的高空间分辨率，所有小棒都能分辨出来。SimPET-X和M7 MRI之间没有明显干扰。SimPET-X提供了具有卓越空间分辨率、灵敏度和计数率性能的高质量小鼠图像。
与SimPET相比，SimPET-X的灵敏度和NECR有显著提高。
