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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。
OBJECTIVE: To investigate the effect of radiation bag fixation on the absorbed dose of tumor. Methods: The difference of absorbed dose between vacuum bag and vacuum bag was measured by simulating source skin distance irradiation (SSD) and simulated isocenter irradiation (SAD), and comparing the difference between the absorbed body surface TPS and the patient contact TPS difference drawn together with the vacuum bag. Results: (1) Simulated isocentre (SAD) When the thickness of the vacuum bag is about 5.2 cm, the difference of absorbed dose is about 1%, which belongs to the clinically acceptable range. When the thickness of the vacuum bag is 12 cm, The difference in measured absorbed dose reached 3%. ② The simulated source distance (SSD) difference between the two groups of data reached more than 10%. ③ simply draw the surface of the patient’s TPS and contact with the patient’s vacuum bag to draw the TPS difference reached 20% to 30%. Conclusions: The vacuum bag has certain influence on the absorbed dose of the tumor during radiotherapy, especially when the thickness exceeds 6 cm, some correction parameters should be added when calculating the dose. In the process of three-dimensional conformal radiotherapy, the outline of the body surface must be vacuum The outline of the bag is also drawn together, making the plan closer to the actual treatment process, the tumor absorbed dose is more in line with clinical requirements.