MV级EPID成像中靶材料与厚度的优化选择

Optimization of Material and Thickness of Accelerator Target for Megavoltage Electronic Portal Imaging Device

摘要: MV级电子射野成像系统（EPID）产生的图像相对于kV级对比度差，其中靶的材料和尺寸是一重要因素。采用Monte-Carlo软件包Geant4程序对6 MV医用直线加速器进行模拟，对MV级EPID成像中靶材料与厚度进行优化选择。计算结果表明，低原子序数的薄靶有利于改善成像质量，在无均整器的情况下，3 mm厚的Cu靶或10 mm厚的Al靶更适用于6 MV的电子射野成像系统。

Abstract: Megavoltage electronic portal imaging device(EPID)suffers from poor quality images comparing to those produced with kilovoltage X-rays. The main factors impacting image quality include the target size and material. The target thickness and material on a 6 MV medical linear accelerator were optimized to maximize the image quality by using Geant4 Monte-Carlo simulation. A simple model of the whole imaging chain was developed for investigation of the effect of the target parameters on the quality of the image. The results show that the low-atomic number (Z) and thin targets make a improve contrast in EPID image. The 6 MV EPID electron mode with a 3 mm copper or 10 mm aluminum target is more suitable without flattening filtration.