精确放疗中热塑定位材料对皮肤表面剂量的影响

The Effect of Home-made Thermoplastic Mask on the Surface Dose of Skin in Precise Radiotherapy

目的:研究不同能量射线治疗机照射下国产热塑膜对患者皮肤表面剂量的影响。方法:采用TQ-2000多通道剂量仪,环状半导体探测器,半导体探头灵敏测量芯片外裹1mm环氧聚酯,PMMA验证模体,西门子Primus-H加速器,国产热塑膜,测量无孔拉伸状2mm厚度、无孔原状2.4mm厚度和网状拉伸状2mm厚度三种形状和厚度的热塑膜在不同射野面积下对皮肤表面剂量的影响。结果:戴上热塑膜比不戴热塑膜皮肤表面剂量增量,按无孔原状、无孔拉伸状和网状拉伸状顺序排列,6MV,5cm×5cm射野分别增加29.5%,25.5%,23.9%;10cm×10cm射野分别增加27.1%,23.8%,22.3%;15cm×15cm射野分别增加24.5%,20.8%,19.6%;15MV时,5cm×5cm射野分别增加41.2%,35.5%,32.1%;10cm×10cm射野分别增加37.8%,32.6%,30.0%;15cm×15cm射野分别增加30.1%,25.8%,23.9%。结论:通过两种不同能量射线的比较,射线能量越高对皮肤表面剂量的影响越大,热塑膜种类固定情况下,射野越小影响越大。热塑膜越薄且有网孔的,其对皮肤表面剂量的影响相对较小。在射野大小一定的情况下,热塑膜对皮肤表面剂量影响从大到小的顺序依次为无孔原状、无孔拉伸状、网状拉伸状。在临床上怎样保护皮肤和在TPS(治疗计划)中怎样修正剂量值应该予以重视。

[ Abstract] Objective： To investigate the influence of thermoplastic masks on the surface dose of skin under differ-ent radiation energy. Methods： Multichannel TQ-2000 dosimeter, semiconductor detectors, PMMA phantom, Siemens Primus-H accelerator, home-made thermoplastic mask including 2mm in thickness stretching membrane without holes, original 2. 4mm in thickness membrane without holes and 2mm in thickness stretching mesh mask were adopted in this stud-y. The influence of these masks on the radiation dose on the surface of skin in different radiation field size was measured. Results：Comparing the surface dose increment between the condition of wearing and not wearing a mask in accordance with the order of original mask without holes, stretching membrane without holes, and stretching mesh mask, the dose increment was 29. 5%,25. 5% and 23. 9% respectively when field size was 5cm＆#237;5cm, 27. 1%,23. 8% and 22. 3% when field size was 10cm＆#237;10cm, 24. 5%,20. 8% and 19. 6% when field size was 15cm＆#237;15cm under 6MV radiation energy;41. 2%, 35. 5% and 32. 1% when field size was 5cm ＆#237;5cm; 37. 8%,32. 6% and 30.0% when field size was 10cm ＆#237;10cm;30.1%,25. 8% and 23. 9% when field size was 15cm＆#237;15cm under 15MV radiation energy. Conclusion： The effect of mask on the surface dose of skin increases along with the increasing of radiating energy and decreases along with the in-creasing of field size. The influence on the surface does of skin is relatively lower when thinner mesh masks are applied. Under fixed field size, the influence increases in the sequence of original membrane without holes, stretching mask without holes, and stretching mesh mask. How to protect skin and revise dose distribution in TPS treatment planning should be paid more attention to in clinical practice.