面罩对不同射线治疗剂量影响的探讨  

Impact of thermoplastic mask on dosimetry of different radiotherapeutic beams

作　　者：陈立新[1] 张黎[1] 钱剑扬[1] 黄晓延[1] 卢杰[1] 黄劭敏[1] 

机构地区：[1]中山大学附属肿瘤医院放射治疗科,广州510060

出　　处：《中华放射肿瘤学杂志》2003年第1期55-57,共3页Chinese Journal of Radiation Oncology

摘　　要：目的　测量在光子线及电子线照射下面罩对治疗剂量的影响。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。采用三维水箱测量电子线射野中心轴百分深度剂量 ,并利用平行板电离室对特定深度进行验证。结果　加上面罩后 ,8MV光子线建成区剂量有明显增加 ,近表面处相对增加约 2 5 %左右 ;8、1 2和 1 5MeV的电子线的中心轴百分深度剂量曲线则普遍前移。结论　对于光子线主要考虑的是近表面建成区剂量的改变 ;对电子线则要考虑由于百分深度量前移而可能影响治疗靶区的最小剂量。三维适形放射治疗中要注意治疗计划系统 (TPS)的计算结果是否考虑面罩对治疗剂量的影响。Objective To determine the influence of auxiliary thermoplastic mask on dose distribution of photon or electron beams. 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. Using 3-D water phantom, the central axis perce n tage depth doses(PDD) of electron beams were measured with verification of the p arallel-plate ionization chamber at several given depths. Results When 8?MV X-ray was delivered through the added facial mask, the buildup region doses were incr eased obviously with a 25% relative increment beneath near the surface. When 8, 12, 15?MeV electron beams and mask were used, all PDD curves moved to the surfa ce. Conclusions The impact of thermoplastic mask on the dose increase in the X-ray buildup region, and on the PDD decrease in the electron beam target region shou ld be paid much more attention. And the dose distribution,with an added mask,wil l have to be re-evaluated in 3-D conformal radiotherapy.

关 键 词：面罩 放射疗法 剂量测量 

分 类 号：R815[医药卫生—放射医学]