真空袋对肿瘤吸收剂量的影响

目的:探讨放疗固定设备真空袋对肿瘤吸收剂量的影响。方法:通过模拟源皮距照射(SSD)和模拟等中心照射(SAD),测定使用真空袋和不使用真空袋时吸收剂量的差别,及比较单纯画出病人体表TPS和与病人接触接触的真空袋一起画出的TPS的差别。结果:①模拟等中心照射时(SAD)如果真空袋的厚度在5.2 cm左右时,测量出的吸收剂量差别在1%附近,属于临床可接受的范围,而真空袋的厚度在12 cm时,测量出的吸收剂量差别就达到了3%。②模拟源皮距照射(SSD)两组数据差别达到了10%以上。③单纯画出病人体表的TPS和与病人接触的真空袋一起画出的TPS的差别达到了20%~30%。结论:真空袋在放疗中对肿瘤吸收剂量有一定的影响,尤其是在厚度超过6 cm时,计算剂量时应该加入一定的校正参数;三维适形放疗时在勾画体表轮廓时一定要将真空袋的轮廓也一起画出,使得计划更加接近真实的治疗过程,肿瘤吸收剂量才更能符合临床的要求。

The Effect of Vaccun Bag on Tumour Absorption Dose

Objective To evaluate the effect of vaccum bag on tumour absorption dose.Methods By the source-skin distance(SSD) technique and the source-axis distance(SAD)technique,the tumour absorption doses in drawing outline of the Vaccum bag and in subtracting outline of the vaccum bag are detected respectively.The differences of the treatment planning in drawing outline of the patient and in delineating the outline of the vaccum bag are compared.Results for experiment 1,when the thickness of vaccum bag is 5.2cm,The difference of the tumour absorption dose in drawing outline of the vaccum bag and in subtracting outline of the vaccum bag is about 1%.when the thickness of vaccum bag is 12cm,the difference is 3%.For experiment 2,by mimic SSD technique,the difference of tumour absorption dose in drawing outline of the vaccum bag and in subtracting outline of the vaccum bag is over 10%.For experiment 3,the difference of(Mu) in drawing the outline of the patient and in delineating vaccum bag is 20%-30%.Conclusion The effects of vaccum bag on the tumour absorption dose are determined.When the thickness of vaccum bag is over 6cm,rectifying parameters should be added to the tumour absorption dose.The outline of the vaccum bag should be drawed in three-dimensional conformal radiation treatment plan.