基于CdZnTe像素阵列探测技术的伽玛源成像

Gamma source imaging based on pixellated CdZnTe detection

根据高能射线针孔成像理论,采用CdZnTe像素阵列探测器建立了直接成像探测模式的伽玛源针孔探测系统。测试分析了CdZnTe像素阵列探测器的能量分辨力及峰值效率,讨论研究了针孔成像探测系统的调制传递函数和附加噪声特性,测试获得直径5mm137Cs源的探测图像,采用Lucy-Richardson迭代算法得到了137Cs源的复原图像。实验结果表明:CdZnTe探测器对662keV137Cs源的能量分辨力为6.25%～7.50%,峰值效率65.0%～72.5%;成像系统探测图像存在一定扩散现象,所采用的Lucy-Richardson迭代复原算法能较好地修正图像扩散,提高探测图像中心区域细节分辨力;估算所得137Cs源尺寸误差约0.5mm,所建立的CdZnTe针孔成像探测系统能有效得到小尺寸伽玛源的辐照强度分布及尺寸信息。

A gamma source pinhole imaging system with direct imaging mode pixellated CdZnTe detector has been constructed based on the principle of pinhole imaging. The energy resolution and peak efficiency of CdZnTe pixellated detector were tested and analyzed. During the preliminary experiments,modulation transfer function （MTF） and additional noise characteristic of pinhole imaging system were investigated and discussed. This paper presents and evaluates the test images of a 0.5 mm diameter 137Cs gamma source. The measured pinhole images are restored with the Lucy-Richardson algorithm. The energy resolution of the CdZnTe pixellated detector system for 662 keV 137Cs are 6.25%～7.50% and photon peak efficiency are 65.0%～72.5%. There is lateral spread information in the source images tested by the CdZnTe detector and degraded images can be restored appropriately with the application of Lucy-Richardson algorithm. Inner area spatial resolution gets improved through the restoration method and the estimated source diameter has an error of 0.5 mm.