射波刀蒙特卡罗剂量计算算法射束模型的调试

Commissioning the Beam Model for the Cyberknife Monte Carlo Dose Calculation Algorithm

目的建立和调试医院新引进的射波刀蒙特卡罗剂量计算算法射束模型,确保治疗计划系统算法的精度,以便后期更好地投入临床使用。方法通过比较测量值和蒙特卡罗模拟值在离轴比(OCR)半影区的偏差,选定最终源尺寸的大小,然后利用准直器校正因子和能量校正因子对组织模体比(TPR)和OCR反复迭代、修正,最终使得各项指标偏差均小于±2%。结果经调试后,光子源半峰全宽(FWHM)值选取为1.4 mm,且所有准直器所有深度处的TPR、OCR及所有源轴距(SAD)的输出因子(OF)误差均在±2%内。结论通过对医院最新引进的VSI型射波刀蒙特卡罗剂量计算算法射束模型的调试,各项指标偏差值均在±2%内,满足临床要求。

Objective The beam model of Monte Carlo dose calculation algorithm for Cyberknife which was introduced in our hospital was built and commissioned.By this way,we could ensure the treatment planning system algorithm accuracy,so that it could be put into clinical use better.Methods Choosing the suitable Gaussian source size according to the comparison of the penumbra widths of the Monte Carlo calculated OCR and the measured OCR.In order to ensure the deviation of TPR and OCR between Monte Carlo calculated and the measured less than±2%,the factors of ECF and CCF were used repeatedly to iterate and correct TPR and OCR.Results After commissioning and correction,the slight deviations were observed between the values of Monte Carlo calculated and measured for TPR,OCR and OF,and the deviation values were less than±2%.The proper Gaussian source size was 1.4 mm.Conclusion After building and commissioning the beam model for the Cyberknife Monte Carlo dose calculation algorithm,the objective deviations value of all indicators was less than±2%and met the clinical requirements.