Objective To verify the dose of constant dose rate (CDR)-volumetric modulated arc therapy (VMAT) plan on Varian clinical 23EX linear accelerator using MapCheck phantom (Sun Nuclear Company).Methods RayStation treatment planning system was used to design CDR-VMAT plans on Varian clinical 23EX linear accelerator for randomly selected 10 lung cancer patients and 10 rectum cancan patients,with dose rate of 200 MU/min.Two dual arcs from 182 to 178 degrees of 6 MV were used for lung cancer patients,while two dual arcs from 230 to 130 degrees of 10 MV were applied for rectum cancer patients.The coronal and sagittal setups of MapCheck phantom were used separately for measuring coronal and sagittal dose distributions.The gamma passing rates on coronal and sagittal planes were evaluated.Results Based on the 3 mm/3％ criteria,the distance to agreement and gamma passing rates of 6 MV plans for lung cancer were (95.30±2.91)％ and (96.82±2.40)％,respectively,and those of 10 MV plans for rectum cancer were (95.03±4.05)％ and (97.48±2.78)％,respectively.The delivery time for each treatment plan was about 3 minutes.Conclusion Using the coronal and sagittal setups of MapCheck phantom separately for the verification of coronal and sagittal dose distributions has potential for the dose verification of CDR-VMAT plan on Varian clinical 23EX linear accelerator.%目的:应用Sun Nuclear公司的MapCheck二维半导体阵列对Varian Clinical 23EX加速器固定剂量率旋转调强计划进行验证.方法:随机选择10例肺部肿瘤患者和10例直肠肿瘤患者,使用RayStation计划系统在Varian Clinical 23EX加速器上制定固定剂量率旋转调强计划,其中肺部患者使用182°到178°及其对偶的两个6MV能量的治疗弧,直肠患者使用230°到130°及其对偶的两个10MV能量的治疗弧,剂量率均为200 MU/min.使用MapCheck在治疗床上水平放置测量冠状面的剂量分布,竖直放置测量矢状面的剂量分布,分别评估每个放疗计划在冠状面和矢状面的剂量验证通过率.结果:使用(3mm,3％)标准,肺部6MV计划的DTA和Gamma通过率为(95.03±2.91)％和(96.82±2.40)％,直肠10MV计划的DTA和Gamma通过率为(95.30±4.05)％和(97.48±2.78)％.单个患者计划执行时间约为3min.结论:使用MapCheck的水平和竖直两种摆位方式进行旋转调强计划的冠状位和矢状位剂量分布验证,或许可以作为Varian Clinical 23EX加速器固定剂量率旋转调强放疗计划验证的可选方法之一.
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