6MV X线时组织等效补偿膜与人体空气间隙对表面剂量的影响

摘要

目的:研究6MV X线时组织等效补偿膜与人体空气间隙时表面剂量的影响.方法:使用瓦里安23EX直线加速器6MV X-线,分别放15、10、15mm Superflab等效组织补偿膜于平板电离室上,改变等效组织补偿膜与泡沫表面空气间隙至0、5、10、20、30、40、50 mm,相同其他条件测量,记录静电仪读数并归一于各厚度补偿膜0 mm空气间隙测量值.结果:很小的空气间隙时(5 mm)表面剂量就有显著下降(10%左右),空气间陈为5～30 mm范围时表面剂量变化较小,之后随空气间陈进一步增大,表面剂量又有较明显下降.结论:使用补偿膜越薄,空气间隙越大,表面剂量下降越大.%Objective To explore the surface dose perturbation due to the air gap between bolus and patient. Methods 6MV X-ray was employed and three kinds of thickness Superflab boluses were put on the parallel ion chamber respectively. The values were written down from the UNIDOS with the different air gaps(0、5、10、20、30、40、50 mm) and were normalized to that of 0mm air gap. Results The surface dose decreases significantly for smaller air gaps(＜5 mm) and larger air gaps (＞30 mm). Conclusion The surface dose deceases for thinner boluses and larger air gaps.