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目的:结合EPID与EUD方法,分析物理几何变化与等效均衡剂量变化确定宫颈癌患者靶区的最佳外放生物边界。方法:选取24例宫颈癌患者,随机均分为2组(A、B组)。A、B组都用EPID测量,记录在x(左右)、y(胸背)、z(头脚)方向上基于等中心的误差坐标数值。在TPS中将此误差坐标数值模拟出来,A组只重新计算剂量;B组根据物理学δ公式,计算PTV外扩x mm后,重新优化计划,再在误差坐标上计算剂量,对比评价A、B组各计划的生物剂量。结果:Matlab模拟EPID测得90%的误差坐标分布近似成椭球体,δ公式计算PTV外扩边界为5 mm;A、B组横向对比结果,在PTV上δ公式具有其正确性,危及器官上存在剂量超量的风险;EUD值计算,B组纵向对比结果,靶区外扩1 mm～2 mm计划在PTV上较外扩5 mm计划稍差,外扩3 mm～4 mm计划较外扩5 mm计划无统计学差异,在危及器官上外扩1 mm～4 mm计划都要优于外扩5 mm计划。结论:在宫颈癌的调强放疗中,基于使用EPID与EUD方法确定靶区的最佳生物边界具有一定的借鉴意义。
OBJECTIVE: To determine the best exoplanet boundary of cervical cancer patients by combining EPID and EUD methods to analyze the change of physical geometry and equivalent equal dose. Methods: Twenty-four patients with cervical cancer were randomly divided into two groups (group A and group B). Group A and B were measured with EPID and the isocenter-based error co-ordinates were recorded in x (left and right), y (chest and back), z (head and foot) directions. In TPS, the error coordinates were numerically simulated, and group A only recalculated the dose. In group B, according to the formula of physics δ, after calculating the expansion of PTV x mm, the plan was re-optimized and the dose was calculated on the error coordinates. Group B bio-dose plan. Results: The error distribution of 90% error of the simulated EPID by Matlab was approximately ellipsoid. The formula of δ was used to calculate the extension boundary of PTV was 5 mm. The lateral comparison results of group A and B showed that δ formula on PTV had its correctness, There was a risk of overdosing. The EUD value calculated by longitudinal comparison in group B showed that the plan of 1 mm ~ 2 mm outside the target area was slightly worse than the 5 mm extension plan of PTV, and the plan of outward expansion of 3 mm ~ 4 mm was more outward The 5 mm plan had no statistical difference, and the plan of 1 mm ~ 4 mm outside the organ at risk of outgrowing was superior to the plan of 5 mm extension. Conclusion: In the IMRT of cervical cancer, it is of certain referential significance based on the use of EPID and EUD to determine the optimal biological boundary of target.