基于康普顿散射效应的双层辐射热点探测技术研究

This project is based on the compton scattering effect of gamma ray, to detection and locate the radiological hot spot with two layers of detection.The research includes two points: the first one is to simulate different senarios of two layers compton scattering system with position sensitive detectors for Monte-Carlo simulation. The calculation consists of the detection efficiency of recoiled election and scattering ray under different materials, geometry or arrays of crystals. The simulations provide guide and optimization for prototype design. The second point is focus on the methodology of image reconstruction. This work tries to project the hot spot location on the image plate with cone angle caculated from the compton scattering detection.This work will play an important role for radiological hot spot detection in domestic. The researching achievements will provide reference for esteblishing gamma immage detection system which stems from two layers compton scattering effect.

本课题基于伽马射线的康普顿散射效应，利用双层探测器实现对辐射热点的探测与定位。研究内容包括两个方面：第一，利用蒙特卡洛方法模拟不同位置灵敏探测器组成的康普顿散射系统，计算在不同材料、几何、晶体空间阵列条件下的康普顿反冲电子和散射电子被探测到的效率，用来优化探测器的设计。第二，开展基于康普顿散射的热点探测算法研究，本研究基于康普顿散射公式建立入射角，利用计算圆锥角在成像平面的投影圆环焦点重建热点位置。本课题将在很大程度上弥补国内在辐射热点探测技术上的空白，研究成果对建立基于康普顿散射的双层辐射热点探测系统具有重要参考意义。

本文模拟了康普顿散射成像系统，实现了利用双层碲锌镉探测器对γ放射源的精确探测成像。研究利用蒙特卡罗计算程序Geant4对探测器系统进行模拟，结果记录产生的康普顿事件分别在散射层和吸收层的能量和位置信息。通过对多个康普顿事件的计算，在成像平面区域反投影出康普顿圆环的叠加图像。为提高成像的精确度，研究中通过最大似然估计期望最大法(ML-EM)和随机起点集合算法（SOE）对反投影图像进行重建，分别在迭代200次和300次后实现了对热点位置的精确定位。