Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, Korea.
J Nucl Med. 2012 Apr;53(4):608-14. doi: 10.2967/jnumed.111.097501. Epub 2012 Mar 13.
The most investigated semiconductor photosensor for MRI-compatible PET detectors is the avalanche photodiode (APD). However, the silicon photomultiplier (SiPM), also called the Geiger-mode APD, is gaining attention in the development of the next generation of PET/MRI systems because the SiPM has much better performance than the APD. We have developed an MRI-compatible PET system based on multichannel SiPM arrays to allow simultaneous PET/MRI.
The SiPM PET scanner consists of 12 detector modules with a ring diameter of 13.6 cm and an axial extent of 3.2 cm. In each detector module, 4 multichannel SiPM arrays (with 4 × 4 channels arranged in a 2 × 2 array to yield 8 × 8 channels) were coupled with 20 × 18 Lu(1.9)Gd(0.1)SiO(5):Ce crystals (each crystal is 1.5 × 1.5 × 7 mm) and mounted on a charge division network for multiplexing 64 signals into 4 position signals. Each detector module was enclosed in a shielding box to reduce interference between the PET and MRI scanners, and the temperature inside the box was monitored for correction of the temperature-dependent gain variation of the SiPM. The PET detector signal was routed to the outside of the MRI room and processed with a field programmable gate array-based data acquisition system. MRI compatibility tests and simultaneous PET/MRI acquisitions were performed inside a 3-T clinical MRI system with 4-cm loop receiver coils that were built into the SiPM PET scanner. Interference between the imaging systems was investigated, and phantom and mouse experiments were performed.
No radiofrequency interference on the PET signal or degradation in the energy spectrum and flood map was shown during simultaneous PET/MRI. The quality of the MRI scans acquired with and without the operating PET showed only slight degradation. The results of phantom and mouse experiments confirmed the feasibility of this system for simultaneous PET/MRI.
Simultaneous PET/MRI was possible with a multichannel SiPM-based PET scanner, with no radiofrequency interference on PET signals or images and only slight degradation of the MRI scans.
最常用于 MRI 兼容 PET 探测器的半导体光电传感器是雪崩光电二极管 (APD)。然而，硅光电倍增管 (SiPM)，也称为盖革模式 APD，由于其性能优于 APD，因此在下一代 PET/MRI 系统的开发中受到关注。我们已经开发了一种基于多通道 SiPM 阵列的 MRI 兼容 PET 系统，以允许同时进行 PET/MRI。
SiPM PET 扫描仪由 12 个探测器模块组成，其直径为 13.6cm，轴向长度为 3.2cm。在每个探测器模块中，4 个多通道 SiPM 阵列（以 2x2 阵列排列的 4x4 个通道，产生 8x8 个通道）与 20x18Lu(1.9)Gd(0.1)SiO(5):Ce 晶体（每个晶体为 1.5x1.5x7mm）耦合，并安装在电荷分配网络上，将 64 个信号多路复用到 4 个位置信号。每个探测器模块都封装在一个屏蔽盒中，以减少 PET 和 MRI 扫描仪之间的干扰，并监测盒内温度以校正 SiPM 的温度相关增益变化。将 PET 探测器信号路由到 MRI 室外部，并使用基于现场可编程门阵列的数据采集系统进行处理。在装有内置到 SiPM PET 扫描仪中的 4cm 环形接收器线圈的 3-T 临床 MRI 系统内进行 MRI 兼容性测试和同时进行的 PET/MRI 采集。研究了成像系统之间的干扰，并进行了体模和小鼠实验。
在同时进行的 PET/MRI 中，没有观察到 PET 信号的射频干扰，也没有观察到能谱和洪水图的退化。带有和不带有工作 PET 的 MRI 扫描质量仅略有下降。体模和小鼠实验的结果证实了该系统同时进行 PET/MRI 的可行性。
使用基于多通道 SiPM 的 PET 扫描仪可以实现同时进行的 PET/MRI，不会对 PET 信号或图像产生射频干扰，也不会对 MRI 扫描产生明显的降级。
