调强放疗中多叶准直器漏射线对晶体受照剂量的影响

摘要

目的 研究多叶准直器( MLC)的漏射线及其对晶体的影响.方法 使用PTW30013电离室测量MLC的透射因子,并针对5例头部肿瘤患者的调强计划,用PTW31010电离室在Topslane圆柱形模体中,对晶体受照剂量做验证测量.结果 MLC透射因子是1.42％,符合临床要求,5例患者晶体实测剂量均高于计划计算值(P＜0.05).结论 调强放疗中MLC的漏散射线,会使晶体实际受照剂量比计划值偏高,在特殊情况下,可以增加对危及器官的剂量验证测量.%Objective To study the impact of MLC dose leakage on lens in 1MRT. Methods MLC transmission factor was measured with PTW 30013 ion chamber, and the dose verification for lens of 5 IMRT plans were performed in the Topslane cylinder phantom using PTW 31010 ion chamber. Results MLC transmission factor was 1.42% and the measured doses of lens were more than calculated values (P<0.05). Conclusion MLC leakage and scattered ray on lens result in the higher dose than calculated value. It is suggested that the verification measurement of organs at risk should be performed in some cases.