摘要
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： Investigating the EPID combined with the EUD method, to analyse the best biological margins of target of patients with cervical cancer with changes of physical geometry and changes of equivalent uniform dose. Methods： 24 cases of patients with cervical cancer are selected and divided into 2 groups （group A,B） randomly. Both A and B groups use EPID method, EPID measures the distribution of the errors and the coordinates of the errors regress TPS and are simulated in TPS, group A recalculates the plans; Group B calculates the expanding x mm according to physical δ formula, reoptimizates the plans and calculates the dose in the coordinates of the errors. Compare and evaluate the biological dose of group A,B of each plan. Results： 90% of the coordinates of the errors which measured with EPID distribute approximately like an ellipsoid, δformula calculates PTV expanding to 5 mm; Transverse comparison results of Group A and B, δ formula has its correctness on the PTV, jeopardize dose levels of risk on the OARs; EUD value calculation, the longitudinal comparison results of group B, expanding 1 ram-2 rnm plans on the biological dose of PTV worse than 5 mm plans, expanding 3 mm-4 mm plans is no statistical difference with 5 mm plans. Expanding 1 mm-4 mm plans is all better than 5 mm plans on the biological dose of OARs. Conclusions： With intensity modulated radiation therapy of cervical cancer, combination of EPID and EUD methods to determine the best biological margin has certain reference significance.
出处
《中国医学物理学杂志》
CSCD
2013年第5期4378-4382,共5页
Chinese Journal of Medical Physics
