一种估算静态MLC调强放疗治疗时间的方法

Estimate the Delivery Time of Static MLC-based IMRT

目的:本研究针对静态多叶准直器(MLC)调强放疗技术,分析影响治疗时间的各种因素,建立数学模型估算治疗时间,为临床评价计划执行效率提供一个工具。方法:以Varian600CD加速器为研究对象,计划采用Philips公司Pin-nacle3(v8.0)计划系统设计。将静态MLC调强放疗的治疗时间T分为4个部分:射线照射时间TMU、MLC走位时间TMLC、原射野准备时间TPOB和分野准备时间TPAB。求出各部分的线性函数表达式,即可得到治疗时间的模拟公式。在VARIS治疗记录中可查到两项有关治疗时间的历史记录,一项是每个射野中所有子野的MLC走位和射线照射时长,另一项是该射野的结束时刻。利用这两个时间数据,从系统中随机抽取30例典型病例作为样本病例,线性拟合确定其他各项的线性系数,即可求出治疗时间表达式。结果:治疗时间估算公式T=MU/DR+(NBS-NOB-NAB)×2.98+GA/5.78+(NOB-1)×17.58+NAB×26.95。采用另外6例病例验证估算公式,得到治疗时间计算值与实际值的比值分别为:1.03,0.92,1.13,0.99,0.99,1.06。结论:对于静态MLC调强放疗计划,影响治疗时间的主要因素为射野和子野的个数。在满足临床剂量要求的前提下,减少射野和子野的个数,能明显减少治疗时间。

Objective: To analyze the influence factors of static MLC-based IMRT plans' delivery time and make a simulant formula to estimate it.Methods: Taking Varian 600CD as the object linac and Pinnacle3(v8.0) as the treatment plan system,the delivery time of static MLC-based IMRT plan was divided into four parts: beam-on time,MLC moving time,prepare time of original beams and prepare time of additional beams.If we got every part's linear function expression,we got the formula.Each beam's MLC moving time / beam-on time and the ending time could be got from treatment history.The other data of delivery time could be reckoned through these two data.In this study,30 patients' treatment time data were used to get the coefficients of the formula.Results: The final formula was T = MU/DR+(NBS-NOB-NAB)×2.98+GA/5.78+(NOB-1)×17.58+NAB×26.95.The other 6 patients' plan parameters were used to validate this formula.The rates of the calculating values and the real values were 1.03,0.92,1.13,0.99,0.99,and 1.06.Conclusions: The main factors which influence delivery time of static MLC-based IMRT are beam numbers and segment beam numbers.Reducing beam and segment beam numbers can obvious reduce delivery time on the condition that dose distribution still conform to the clinic and physical criterion.