PD与Dolphin验证系统在乳腺癌调强放疗计划剂量验证中的应用

Application of PD and Dolphin in Dose Verification of Intensity Modulated Radiation Therapy Plans for Breast Cancer

目的研究PD(portal dosimetry)与Dolphin在乳腺癌调强放疗计划剂量验证中的应用。方法选取12例左侧乳腺癌调强放疗计划,分别采用加速器自带的非晶硅射野影像系统PD和IBA公司的Dolphin穿透电离室矩阵进行剂量验证,对比分析其通过率、评估点数及未通过区域,运用γ分析验证两者剂量分布的一致性。差异指标包括γ通过率(3%/3 mm,TH=10%和2%/2 mm,TH=10%),靶区剂量参数D_(1)、D_(mean)、D_(99)与危及器官剂量参数D_(1)、D_(mean)等。结果采用γ(3%/3 mm)标准进行分析时两种验证系统的平均通过率均在95%以上,采用γ(2%/2 mm)标准进行分析时两种验证系统的平均通过率均在90%以上,都能满足临床要求,PD组的验证结果明显高于Compass计算组和Dolphin测量重建组,差异有统计学意义(P<0.05)。PTV对应的D_(1)、D_(mean)和D_(99)采用Compass计算和Dolphin测量重建均存在统计学差异(P<0.05),平均差异值范围在5%以内;对于危及器官中左肺和心脏的D_(1)和D_(mean)的比较,只有心脏的D_(mean)差异较大,存在统计学差异(P<0.05),其余均无统计学差异。结论两种设备均能有效验证直线加速器对放疗计划的执行能力,PD是一个方便用于验证调强放疗计划的理想二维验证设备,Dolphin三维验证系统的独立核算和实测重建可以全面的分析理论与实际照射剂量差异,为乳腺癌调强放疗计划的准确实施提供参考依据。

Objective To study the application of Portal Dosimetry and Dolphin in the dose verification of IMRT plans for breast.Methods 12 cases of left breast cancer IMRT plans were selected.The dose verification was performed using amorphous silicon radiation field imaging system PD and IBA's Dolphin penetration ionization chamber matrix,respectively.The pass rate,assessment points and failed regions were compared and analyzed,and the consistency of dose distribution were verified by gamma analysis.Difference indicators include γ passing rate(3%/3 mm,TH=10% and 2%/2 mm,TH=10%),target dose parameters D_(1),D_(mean),D_(99) and organ-at-risk dose parameters D_(1),D_(mean),etc.ResuIts The mean pass rates of both validation systems were above 95% when the γ(3%/3 mm)criterion was used for analysis and above 90% when the γ(2%/2 mm)criterion was used for analysis,both of which could meet the clinical requirements,and the validation results of the PD group were significantly higher than those of the Compass calculation group and the Dolphin measurement reconstruction group,and the difference was statistically significant(P<0.05).The D_(1),D_(mean) and D_(99) corresponding to PTV were statistically different by Compass calculation and Dolphin measurement reconstruction(P<0.05),and the average difference was within 5%.For the comparison of D_(1) and D_(mean) between left lung and heart in organs-at-risk,only the D_(mean) of heart was significantly different(P<0.05),while the others were not statistically different.Conclusion Both devices can effectively verify the ability of linear accelerators to perform radiotherapy plans.PD is an ideal 2D verification device for verifying IMRT plans.More specific information about the target and OAR can be provided by the Dolphin 3D verification system,which is helpful for the safe implementation of IMRT plans for breast cancer.