We characterize a compact MR-compatible PET insert for simultaneous preclinical PET/MRI. Although specifically designed with the strict size constraint to fit inside the 114-mm inner diameter of the BGA-12S gradient coil used in the BioSpec 70/20 and 94/20 series of small-animal MRI systems, the insert can easily be installed in any appropriate MRI scanner or used as a stand-alone PET system. Methods: The insert consists of a ring of 16 detector-blocks each made from depth-of-interaction–capable dual-layer-offset arrays of cerium-doped lutetium-yttrium oxyorthosilicate crystals read out by silicon photomultiplier arrays. Scintillator crystal arrays are made from 22 × 10 and 21 × 9 crystals in the bottom and top layers, respectively, with respective layer thicknesses of 6 and 4 mm, arranged with a 1.27-mm pitch, resulting in a useable field of view 28 mm long and about 55 mm wide. Results: Spatial resolution ranged from 1.17 to 1.86 mm full width at half maximum in the radial direction from a radial offset of 0–15 mm. With a 300- to 800-keV energy window, peak sensitivity was 2.2% and noise-equivalent count rate from a mouse-sized phantom at 3.7 MBq was 11.1 kcps and peaked at 20.8 kcps at 14.5 MBq. Phantom imaging showed that features as small as 0.7 mm could be resolved. ¹⁸F-FDG PET/MR images of mouse and rat brains showed no signs of intermodality interference and could excellently resolve substructures within the brain. Conclusion: Because of excellent spatial resolvability and lack of intermodality interference, this PET insert will serve as a useful tool for preclinical PET/MR.

我们的特点是紧凑的MR兼容PET插入物，用于同时进行临床前PET / MRI。尽管专门设计有严格的尺寸限制，以适合在BioSpec 70/20和94/20系列小动物MRI系统中使用的BGA-12S梯度线圈的114毫米内径，但可以轻松地将插件安装在任何合适的MRI扫描仪或用作独立的PET系统。方法：插入物由一个由16个检测器块组成的环组成，每个检测器块均由具有相互作用深度的双层偏置阵列构成，这些阵列由铈掺杂的silicon掺杂-钇正氧化硅酸盐晶体制成，并由硅光电倍增管阵列读出。闪烁体晶体阵列分别由底层和顶层的22×10和21×9晶体制成，层厚度分别为6和4 mm，间距为1.27 mm，从而产生了28 mm的可用视场长，约55毫米宽。结果：空间分辨率从0到15毫米的径向偏移范围在径向的一半处的最大宽度为1.17到1.86毫米。在300至800keV的能量窗口范围内，峰值灵敏度为2.2％，鼠标大小的幻影在3.7 MBqq时的噪声等效计数率为11.1 kcps，在14.5 MBq时达到20.8 kcps的峰值。幻像成像表明，可以分辨出小至0.7 mm的特征。小鼠和大鼠脑部的¹⁸ F-FDG PET / MR图像未显示出联运干扰的迹象，可以很好地解析脑部的亚结构。结论：由于出色的空间可分辨性和互模干扰，该PET插入物将成为临床前PET / MR的有用工具。