COMPASS验证系统在放射治疗中的应用研究

Commisioning of the COMPASS System for Clinical Dose Verification

目的:测试COMPASS三维验证系统在临床应用中的可行性。方法:以三维水箱为基准,比较分析COMPASS系统在百分深度剂量(Percentage depth dose,PDD)、输出因子(Output factor,OUF)、离轴曲线(Profile)和绝对剂量等方面的测量数据与三维水箱所测量数据的相关性和一致性;在均匀模体和非均匀模体中验证7例患者的放疗计划,检测COMPASS系统软件的剂量计算精度和剂量重建精度;通过BallBearming模体测试COMPASS系统硬件对加速器等中心的影响。结果:COMPASS系统测量和重新计算的PDD、OUF、Profile与三维水箱测量的数据具有较好的一致性,其绝对剂量偏差均小于2.5%;COMPASS系统软件在均匀模体和非均匀模体中验证7例患者放疗计划的绝对剂量偏差均小于3%,γ通过率不低于93%,重建精度和剂量计算精度接近于计划系统(Teatmentplanning system,TPS);COMPASS系统的硬件不影响等中心的精度,在三个方向上的偏差都小于1mm。结论:COMPASS系统的独立计算功能和剂量重建功能具有类似TPS的精度,可以提供三维的剂量分布信息,为临床治疗提供安全、可靠的技术保障。

Objective： To evaluate the reliability of 3D dose verification system-COMPASS for clinical use. Methods： The data model of COMPASS software was assessed in Percentage depth dose （PDD） , Output factor （ OUF）, Off-axis curves （ Profile ） and the absolute dose by comparing with 3D water tank. The dose calculation function and reconstruction accuracy of COMPASS system software had been evaluated in homogeneous and anthropomorphic phantoms of 7 cases. In order to minimize the measurement error, the effect to the linac isocenter caused by COMAPASS hardware was detected by BallBearing phantom. Results： The PDDs, OUF, Profiles measured by the COMPASS system matched well with the data measured by 3D water tank, and the deviations of absolute dose were below 2. 5% ; the deviation of absolute dose was below 3% when COMPASS system was used to confirm the radiotherapy plan in homogeneous and anthropomorphic phantoms of 7cases. The Gamma Pass Rate was not less than 93%. The accuracy of independent calculation and reconstruction of COMPASS system were close to TPS. Conclusion ： The function of dose reconstruction and independent calculation provided by COMPASS system has the same accuracy with TPS. The 3D dose verification of COMPASS system could offer more abundant and more direct information for dose distribution, and ensure the clinical quality assurance.