Development of DOI detectors by the use of new semiconductor based photo-detectors and their application to wearable PET systems

盖格模式雪崩光电二极管（Si-PM）具有高增益和对静磁场不敏感的特点，是一种很有前途的PET光电探测器，尤其适用于磁共振成像系统。我们开发了一个基于Si-PM的小动物相互作用深度（DOI） PET系统。检测模块采用滨松4x4 Si-PM阵列（S11065-025P）。将衰减时间为~ 45ns: 1.1mm × 1.2mm × 5mm的0.75 mol% Ce和衰减时间为~ 31ns: 1.1mm × 1.2mm × 6mm的0.025 mol% Ce两种类型的LGSO闪烁体沿DOI方向进行光耦合，形成DOI探测器，排列在11 × 9矩阵中，与Si-PM阵列光耦合。采用脉冲形状分析对这两种lgso进行DOI检测。16个探测器块排列成一个直径68mm的环，形成PET系统。空间分辨率为1.6mm FWHM，视场中心灵敏度为0.6%。利用PET系统成功获得了高分辨率的小鼠和大鼠图像。与MRI同时成像是可能的，但信噪比（S/N）有所下降。

Geiger-mode avalanche photodiode(Si-PM) is a promising photodetector for PET, especially for use in a magnetic resonance imaging(MRI) system because it has high gain and is less sensitive to static magnetic field. We developed a Si-PM based depth-of-interaction(DOI) PET system for small animals. Hamamatsu 4x4 Si-PM arrays(S11065-025P) were used for its detector blocks. Two types of LGSO scintillator of 0.75 mol% Ce(decay time :～ 45ns : 1.1mm x 1.2mm x 5mm) and 0.025 mol% Ce(decay time :～ 31ns : 1.1mm x 1.2mm x 6mm) were optically coupled in the DOI direction to form a DOI detector, arranged in 11 x 9 matrix, and optically coupled to the Si-PM array. Pulse shape analysis was used for the DOI detection of these two types of LGSOs. Sixteen detector blocks were ar-ranged in a 68mm diameter ring to form the PET system. Spatial resolution was 1.6mm FWHM and sensitivity was 0.6% at the center of the field-of-view. High resolution mouse and rat images were successfully obtained using the PET system. Simultaneous imaging with MRI was possible with some loss of the signal to noise ratio(S/N).