CAJ | 학술논문

目的基于简单快速蒙特卡罗程序DPM(dose planning method),通过植入照射源模型并改进程序,解决DPM中无法实现任意角度入射和非规则非均匀野模拟的问题,使其成为调强放疗计划系统的实用蒙特卡罗剂量验证工具.方法通过加速器反演出的能谱结合优化给出的强度图模拟加速器的粒子输运过程.使用虚拟点源结合反演出加速器能谱模拟了加速器的照射源部分,基于DPM的粒子输运物理模型,结合调强放疗计划中的照射野强度分布,以及出射粒子的权重与强度图中的强度相结合,实现了算法.结果通过将DPM模拟计算的规则野结果与三维水箱测量数据对比了百分深度剂量(PDD)和百分离轴剂量(OAR),误差在野内＜2％,半影2～3 mm.以及DPM模拟计算非规则野的结果与有限笔形束剂量计算方法FSPB计算结果的对比,趋势符合,γ分析通过率为95.1％,误差都在允许范围内.校验了改进的DPM的功能和计算精度.结论植入简便照射源模型的DPM程序相较于经典蒙特卡罗程序,速度较快,计算精度和时间可以满足临床需求,可以作为调强放疗计划系统中剂量验证工具.
목적 기우간단쾌속몽특잡라정서DPM(dose planning method),통과식입조사원모형병개진정서,해결DPM중무법실현임의각도입사화비규칙비균균야모의적문제,사기성위조강방료계화계통적실용몽특잡라제량험증공구.방법 통과가속기반연출적능보결합우화급출적강도도모의가속기적입자수운과정.사용허의점원결합반연출가속기능보모의료가속기적조사원부분,기우DPM적입자수운물리모형,결합조강방료계화중적조사야강도분포,이급출사입자적권중여강도도중적강도상결합,실현료산법.결과 통과장DPM모의계산적규칙야결과여삼유수상측량수거대비료백분심도제량(PDD)화백분리축제량(OAR),오차재야내＜2％,반영2～3 mm.이급DPM모의계산비규칙야적결과여유한필형속제량계산방법FSPB계산결과적대비,추세부합,γ분석통과솔위95.1％,오차도재윤허범위내.교험료개진적DPM적공능화계산정도.결론 식입간편조사원모형적DPM정서상교우경전몽특잡라정서,속도교쾌,계산정도화시간가이만족림상수구,가이작위조강방료계화계통중제량험증공구.
Objective To build a Monte Carlo dose verification tool for IMRT Plan by implanting an irradiation source model into DPM code and to extend the ability of DPM to calculate any incident angles and irregular-inhomogeneous fields.Methods The virtual source and the energy spectrum unfolded from the accelerator measurement data were used,in combination with optimized intensity maps,to calculate the dose distribution of the irradiation irregular-inhomogeneous field.The irradiation source model of accelerator was substituted by a grid-based surface source.The contour and the intensity distribution of the surface source were optimized by IMRT.The dose calculation was realized by combining the position of the emitter with the fluence map from the IMRT plan.The weight of the emitter was decided by the grid intensity.The direction of the emitter was decided by the combination of the virtual source and the emitting position.The weighted fraction of the emitter was also combined with the flux grid intensity based on the particle transport model of DPM code.Results The accuracy of calculation was verified by comparing with the measured data.It was illustrated that the differences were acceptable (＜ 2％ inside the field,2-3 mm in the penumbra).The dose calculation of irregular field by DPM simulation was also compared with that of FSPB (Finite Size Pencil Beam).The passing rate of gamma analysis was 95.1％ for peripheral lung cancer.The regular field and the irregular rotational field were all within permissible range of error.The calculation time of regular fields were less than 2 h,and that of the test of peripheral lung cancer was 160 min.Conclusions The adapted DPM code with its simple irradiation source model is faster than that with classical Monte Carlo procedure.Its computational accuracy and speed satisfy the clinical requiremcnt,and it can be useful as a Monte Carlo dose verification tool for IMRT Plan.