Truebeam加速器无均整滤过器6MVX射线SBRT治疗计划的剂量验证评估

Dose verification and assessment of stereotactic body radiation therapy plans based on True Beam accelerator with the 6 MV X-ray of flattening filter free

目的：通过Delta4模体验证在Truebeam加速器上执行的体部立体定向放射治疗（Stereotacic Body Radiation Therapy,SBRT）计划,评价SBRT治疗计划执行过程的可靠性。方法：按抽签法在Eclipse10.0治疗计划系统中选取40例SBRT治疗计划,将选取的治疗计划移植到Delta4模体进行剂量计算,得到计算后的剂量分布,再与Delta4模体实际测量得到的剂量分布进行比较,运用γ分析验证两者剂量分布的一致性,以电离室验证治疗计划中心点的绝对剂量。结果：所有Delta4验证的SBRT治疗计划,采用γ（3%,3 mm）标准进行分析时,通过率均〉98%（98.9%~100%）;当用更为严格的γ（2%,2 mm）标准进行分析时,其通过率均〉90%（91.2%~98%）。SBRT治疗计划用电离室在模体中心点处进行的绝对剂量验证,其计算值和测量值的误差均〈2%（-0.8%~1.5%）。结论：在Truebeam加速器上执行的无均整滤过器6MV X射线SBRT治疗计划是安全可靠的,Delta4是一个用于验证无均整滤过器模式弧形旋转治疗计划的理想设备。

Objective To assess the reliability of stereotactic body radiation therapy （SBRT） plan according to the Delta4 phantom verification for the SBRT plan based on TrueBeam accelerator. Methods Forty SBRT plans in Eclipsc 10.0 treatment planning system were randomly selected to be transferred into Delta4 phantom for dose calculation. The calculated dose distribution was compared with the actual measured dose distribution of Delta4 phantom. The correspondence between these two dose distributions was verified by Gamma analysis. And the ionization chamber was applied to verify the absolute dose of the central points in treatment plans. Results Based on the gamma analysis （3%, 3 ram）, the pass rates of all the verified SBRT plans were more than 98% （98.9%- 100%）. Based on the stricter gamma analysis （2%, 2 mm）, the pass rates were all above 90% （91.2%-98%）. In SBRT plan, the ionization chamber absolute dose verification for the central points of Delta4 phantom showed that the errors between calculated results and measured results were less than 2% （-0.8%-1.5%）. Conclusion The SBRT plans based on TrueBeam accelerator with the 6 MV X-ray of flattening filter free is safe and reliable. And Delta4 is an ideal device for the verification of rotation modulated arc therapy plans based on flattening filter free model.