高剂量率后装近距离治疗现在已成为放射治疗的常用方法之一,近距放射治疗计划系统的应用也越来越广泛,主要目的就是通过优化源的驻留位置和时间来改善剂量分布,提高治疗质量。提出了一种连续驻留位置和驻留时间的近距离放疗剂量优化算法。在插值路径为直线、照射源为点源的情况下,首先将驻留时间T看成是位置X的一个连续函数,计算每个参考剂量点的剂量,再用计算剂量和目标剂量值之差的加权平方和为目标函数,然后用复合型调优法求解最优的曲线参数。曲线可以根据具体情况进行分段,得到曲线后再用积分的数值逼近方法将其离散化,得到最终的驻留位置和驻留时间。实验结果表明,本算法不仅避免了负的驻留时间问题,还可使相邻驻留位置的驻留时间更加平滑;在最后的离散化过程中,可以得到不同的驻留位置和驻留时间结果,使计划具有更好的灵活性。Brachytherapy is an anti-tumor treatment by means of radioactive sources that are placed at short distances from the target tumor tissues and becoming more and more widely used.In this paper,we proposed an algorithm to optimize the dwell time of radioactive source for computer-based high-dose-rate afterloading implants planning system of brachytherapy.The dwell time was considered as a continuous function of the dwell position,calculated the dose values of referenced dose points.The minimal difference between these dose values and demanded dose values was used as the objective to get the optimized function parameters.The function curve could be separated to several sects.The optimized curve was dispersed using compound trapezoid formula to get the dwell positions and dwell times.This method could avoid the emergence of negative dwell time,and reduce the dwell time gradient as well.When dispersing the curves,different dwell times and dwell positions could be obtained,which made the brachytherapy treatment plan more flexible.国家自然科学基金资助项目(60371012、60701022
