基于精确准直线阵探测器的康普顿背散射成像仿真
Compton Backscatter Imaging Simulation Based on Precise Collimated Linear Array Detector

常规的康普顿背散射成像图像重建方法有精准对焦法和能谱解析法两种。传统精准对焦法需逐点扫描，扫描时间长并且射线利用率低下；能谱解析依赖高时间分辨率的探测器，获得的能谱数据有限，且重建算法的计算复杂度高，耗时较长。故本文在精准对焦方法的前提上提出基于线阵探测器的康普顿背散射成像系统，使线阵探测器只接收来自固定散射角度且具有固定能量的背散射光子，缩短了探测时长且提高了射线利用率。后续图像重建过程中考虑射线衰减，无需利用能谱数据仅利用线阵探测器收集到的背散射光子数信息即可完成衰减校正，得到待测物体内部各点电子密度进而获得重建图像。本文利用蒙特卡罗方法，建立仿真模型，完成康普顿背散射成像过程的仿真，经理论计算完成衰减校正，得到物体内各点电子密度以及重建后图像。
Conventional Compton backscatter imaging image reconstruction methods include precise focusing and energy spectrum analysis. Accurate focusing requires point-by-point scanning, long scanning time and low ray utilization; energy spectrum analysis relies on high-time resolution detectors, which can obtain limited energy spectrum data, and the reconstruction algorithm has high computational complexity and time-consuming. Therefore, this paper proposes a Compton backscatter imaging system based on a linear array detector on the premise of a precise focusing method. A collimator is installed on each detection unit of the ray source and the linear array detector to determine the incident source and the linear array. After the spatial position of the detector, the linear array detector can only receive backscattered photons from a fixed scattering angle and with a fixed energy, and the object to be measured is divided into several unit blocks. Each unit block is scanned, and each time the linear array detector is scanned, the depth-photon number information of the corresponding unit block can be obtained to complete the backscattered photon positioning. In the subsequent image reconstruction process, the ray attenuation is considered, and the attenuation correction can be completed by using only the backscattered photon information collected by the linear array detector without using the energy spectrum data, and the electron density of each point inside the object to be measured is obtained to obtain the reconstructed image. This paper uses the Monte Carlo method to establish a simulation model to complete the simulation of the Compton backscatter imaging process. After theoretical calculation, the attenuation correction is completed, and the electron density of each point in the object and the reconstructed image are obtained.