剂量计算是放射治疗计划系统的核心,与常用的笔形束剂量计算方法相比,collapsed cone卷积/叠加剂量计算方法具有更高的计算精度,为此我们研究了collapsed cone卷积/叠加剂量计算方法及加速算法,开发了一套基于collapsed cone卷积/叠加剂量计算方法的光子束放射治疗计划系统,并运用蒙特卡罗方法对剂量计算的准确性进行了验证.实验结果表明剂量计算误差与射束能量、射野尺寸以及剂量计算分辨率有关,当天顶角增量和方位角增量分别取3.75.和15.时,对于3～20 cm的方野,剂量计算误差均小于1.5％.所开发的collapsed cone光子束剂量计算方法准确可靠,可望应用于临床.%Dose calculation is one of key issues in radiation treatment planning system. Compared with pencil beam algorithm, dose calculation based on collapsed cone algorithm is more accurate and precise. In this paper, dose calculation based on collapsed cone algorithm was investigated, and a photon radiation treatment planning system was developed and accuracy of dose calculation was verified using Monte Carlo method. The experiments showed that the calculated dose precision was related with beam energy, field size and dose calculation resolution, the mean dose error between collapsed cone algorithm and Monte Carlo algorithm was less than 1.5% for square field of 3 ~ 20 cm with the increment zenith and azimuth at 3.75° and 15°. The developed collapsed cone algorithm is promising in the future clinical application for its accuracy and reliablility.
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