多普勒展宽效应对康普顿相机成像分辨的影响

在重离子癌症治疗中，康普顿相机是一种非常有应用前景的在线监测离子射程的技术。由于康普顿相机使用晶体探测器来确定伽马射线的位置和沉积能量，因此对这些物理量的测量误差会影响康普顿相机的成像分辨率。除了这些测量误差，多普勒展宽效应也会对相机的成像分辨率产生影响。本文使用开源Geant4软件包分别对150和511 keV的伽马射线在几种晶体材料中产生的多普勒展宽效应进行了角分辨模拟。通过对反投影算法的优化和对成像空间中体素的细化，使得康普顿相机的成像分辨率能够达到1.0 mm以上。本工作还基于角分辨标度，推导了一个可快速估计康普顿相机成像分辨率的近似公式。

Effects of Doppler Broadening on Image Resolution for Compton Camera

In heavy-ion cancer therapy, Compton camera is a promising tool for online monitoring of the range of ions. Compton camera uses crystal detectors to determine the positions and deposited energies of the $gamma$-rays. This will further introduce the errors and affect the actual imaging resolution of the Compton camera, due to the involved Doppler broadening effects influencing the image resolution. This work simulates the angular resolution measure originating from the Doppler broadening effects with Geant4 toolkit for 150 and 511 keV gamma, respectively, in different crystal materials. After optimizing the back-projection algorithm and improving the voxel in imaging interspace, the image resolution can be achieved better than 1.0 mm. An approximate formula is also being proposed to evaluate the image resolution based on the angular resolution measure.