放射治疗中热塑体膜对皮肤剂量的影响

目的研究热塑体膜在6MV和16MV光子束治疗肿瘤时对皮肤剂量的影响。方法使用瓦里安2300CD直线加速器,PTW3381平行板电离室。测量条件：200MU,10cm×10cm照射野,100cm源皮距。在有热塑体膜和无热塑体膜的情况下,分别测量模体表面、模体下1、2、3mm处的剂量,分别比较不同条件下相同深度的剂量。结果放置热塑体膜后模体表面的吸收剂量明显高于无热塑体膜时的吸收剂量,6MV光子束时表面增加了36.2%,16MV光子束时表面增加了47.7%（P〈0.01）,模体表面以下1、2、3mm的剂量同样明显增加,但增加的幅度随深度的增加而逐渐减少。结论使用热塑体膜能显著增加皮肤表面剂量,放疗医师在做放疗计划设计时,应考虑到热塑膜对患者皮肤剂量的影响及其生物效应,尽量采用各种措施减少放射性皮肤损伤。

Influence of thermoplastic film on skin dose in radiotherapy

Objective To study the influences of thermoplastic film on skin doses when treating tumors at 6 MV photon beam and 16 MV photon beam. Methods The 2300CD the linear accelerator （Varian） and parallel-plate chamber of PTW3381 were used. The measuring conditions were 200 MU, 10 cm by 10 cm in the radiation field, and 100 cm source skin distance. The doses were measured in the surface of the film, and 1 mm, 2 mm, and 3 mm under the film respectively with thermoplastic film and without it. The doses in the same depth but under different conditions were compared. Results The absorbed dose in the surface of the thermoplastic film was obviously higher than that without thermoplastic one, which increased by 36.2% at 6 MV photon beam and 47.7% at 16 MV photon beam （P 0.001）. The absorbed doses, 1 mm, 2 mm, and 3 mm under the film, were remarkably increased, but with increasing depth, the incremental range gradually slowed down. Conclusion Application of thermoplastic film can significantly increase the dose in the surface of the skin. Therefore, radiotherapy doctor should take into account the influences and the biological effects of thermoplastic film on patient＇s skin dose and endeavor to take a variety of measures to alleviate radiation-induced skin damage when making a plan of radiotherapy.