VMAT患者剂量验证方法的评价分析

目的 比较分析VMAT不同剂量验证方法的γ通过率是否存在差异性。 方法 用Octavius 4D系统对 12例癌症患者不同解剖部位VMAT计划分别进行旋转照射3D剂量分布和2D剂量分布及机架归零2D剂量分布剂量验证,以3%/3 mm和2%/2 mm标准分析γ通过率,并行配对t检验或Wilcoxon符号秩检验。将不同照射方式的2D剂量分布比较分析得到3%/3 mm和2%/2 mm标准的γ通过率。 结果 旋转照射3D剂量分布、2D剂量分布、机架归零2D剂量分布平均γ通过率分别为3%/3 mm时96.03%、96.98%、98.90%(P=0.227、0.000、0.003),2%/2 mm时分别为82.08%、84.04%、90.90%(P=0.379、0.000、0.000)。不同照射方式2D剂量分布比较分析得到平均γ通过率分别为 98.99(3%/3 mm)和93.68%(2%/2 mm)。 结论 VMAT计划在旋转照射条件下对3D剂量分布进行验证,验证结果才能更真实的反映实际照射情况,更具有参考性。

Analysis of VMAT dosimetric verifications with different techniques

Objective To investigate the gamma (γ) passing rates for volumetric-modulated arc therapy (VMAT) dosimetric verification with different techniques.Methods A total of 12 VMAT plans for the treatment of different anatomical sites in cancer patients were chosen.The Octavius 4D system was used to measure the dose distributions in two different settings:the gantry was rotating (three-dimensional (3D) and 2D γ-analysis) and the gantry was fixed at 0°(2D γ-analysis).The γ passing rates were analyzed with 3%/3 mm and 2%/2 mm criteria, using the paired t test or Wilcoxon signed-rank test.The 2D γ passing rates for different irradiation methods were calculated.Results For the 3D and 2D dose distributions obtained at a rotating gantry angle as well as the 2D dose distribution obtained at zero gantry angle, the average γ passing rates were 96.03%, 96.98%, and 98.90% for 3%/3 mm (P=0.227, P=0.000, P=0.003);82.08%, 84.04%, and 90.90% for 2%/2 mm (P=0.379, P=0.000, P=0.000).For the 2D dose distributions obtained with different irradiation methods, the average γ passing rate was 98.99% for 3%/3 mm and 93.68% for 2%/2 mm.Conclusions The VMAT dosimetric verification based on a 3D volumetric dosimeter at a rotating gantry position can be clinically useful for delivery quality assurance (QA), and can achieve the most reliable dose calculation for VMAT, which has more referential values.