铅门设置对宫颈癌术后VMAT计划的剂量学影响

Effect of Jaw Settings on the Dosimetry of VMAT Plan After Cervical Cancer Surgery

目的比较不同铅门设置对宫颈癌术后容积旋转调强放疗(Volumetric Intensity Modulated Arc Therapy,VMAT)计划的剂量学影响。方法选取14例已执行的宫颈癌术后VMAT计划的患者为研究对象,在Eclipse 15.5计划系统中对铅门设置3种情况:固定铅门一侧,另一侧分别设置2﹑3﹑4 cm,射野参数、剂量限值等优化条件不变,重新优化通量和计算剂量得到3种计划:Plan1(2 cm)﹑Plan2(3 cm)﹑Plan3(4 cm)。采用方差分析模型比较3种计划的靶区和危及器官剂量学参数以及机器跳数。结果3种计划靶区的D_(mean)和D_(50%)、危及器官直肠的D_(max)、左侧股骨头的D_(max)和V_(40)比较差异具有统计学意义(P<0.05),Plan1计划组的机器跳数高于其他计划组(P<0.05),3种计划中其余参数的差异无统计学意义(P>0.05)。结论3种铅门固定方案均满足临床要求,铅门较大的计划组Plan2和Plan3的机器跳数更少,可以提高治疗效率及机器执行率,但对于危及器官的保护略弱于铅门较小的Plan1组。

Objective To compare the impact on volumetric intensity modulated arc therapy(VMAT)plans for postoperative cervical cancer with different jaw settings.Methods 14 cases of cervical cancer postoperative VMAT plans were selected,and three settings were made for the jaw in Eclipse15.5 planning system:One side of the jaw was fixed,and the other side was set to 2 cm,3 cm,and 4 cm,respectively.Other optimization conditions such as radiation field and OAR dose constraints remained the same.Three plans were obtained by re-optimizing the flux and calculated dose:Plan1(2 cm),Plan2(3 cm),Plan3(4 cm).Comparison of target volume and organ at risk dosimetry parameters and machine hop count among the three plans by using ANOVA models.Results The dosimetry parameters significantly different were as follows:there were significant differences in D_(mean) and D_(50%) of the target volume,D_(max) of the rectum at risk,D_(max) and V_(40) of the left femoral head among the three plans(P<0.05).In addition,machine jump number in Plan1 was higher than that compared with other plans(P<0.05),and the other parameters were not statistically significant(P>0.05).Conclusion All the treatment plans with three types of jaw settings can meet the clinical requirement.However,Plan2 and Plan3with larger lead have less machine jump number,which can improve the treatment efficiency and machine execution rate,but the protection of organs at risk is slightly weaker than Plan1 with smaller lead.