Methods Using the PTW Marcus 23343 type fixed-separation parallel-plate ionization chamber in a special ph an tom(PMMA), the change of photon dose buildup region was measured with rectificat ion of Bruce empirical formula.

• 方法 采用PTWMarcus2 3343型平行板电离室在专用的有机玻璃模体 (PMMA)中测量光子线建成区剂量的变化情况 ,采用Bruce等介绍的经验公式对测量结果进行修正。