DPM 作为 PRIMO 的辐射传输引擎。
DPM as a radiation transport engine for PRIMO.
机构信息
Centro Médico Paitilla, Calle 53 y ave. Balboa, Panama City, Panama.
Instituto de Investigaciones Científicas y de Alta Tecnología, INDICASAT-AIP, City of Knowledge, Building 219, Panama City, Panama.
出版信息
Radiat Oncol. 2018 Dec 27;13(1):256. doi: 10.1186/s13014-018-1188-6.
BACKGROUND
PRIMO is a dose verification system based on the general-purpose Monte Carlo radiation transport code PENELOPE, which implements an accurate physics model of the interaction cross sections and the radiation transport process but with low computational efficiency as compared with fast Monte Carlo codes. One of these fast Monte Carlo codes is the Dose Planning Method (DPM). The purpose of this work is to describe the adaptation of DPM as an alternative PRIMO computation engine, to validate its performance against PENELOPE and to validate it for some specific cases.
METHODS
DPM was parallelized and modified to perform radiation transport in quadric geometries, which are used to describe linacs, thus allowing the simulation of dynamic treatments. To benchmark the new code versus PENELOPE, both in terms of accuracy of results and simulation time, several tests were performed, namely, irradiation of a multi-layer phantom, irradiation of a water phantom using a collimating pattern defined by the multileaf collimator (MLC), and four clinical cases. The gamma index, with passing criteria of 1 mm/1%, was used to compare the absorbed dose distributions. Clinical cases were compared using a 3-D gamma analysis.
RESULTS
The percentage of voxels passing the gamma criteria always exceeded 99% for the phantom cases, with the exception of the transport through air, for which dose differences between DPM and PENELOPE were as large as 24%. The corresponding percentage for the clinical cases was larger than 99%. The speedup factor between DPM and PENELOPE ranged from 2.5 ×, for the simulation of the radiation transport through a MLC and the subsequent dose estimation in a water phantom, up to 11.8 × for a lung treatment. A further increase of the computational speed, up to 25 ×, can be obtained in the clinical cases when a voxel size of (2.5 mm) is used.
CONCLUSIONS
DPM has been incorporated as an efficient and accurate Monte Carlo engine for dose estimation in PRIMO. It allows the concatenated simulation of the patient-dependent part of the linac and the patient geometry in static and dynamic treatments. The discrepancy observed between DPM and PENELOPE, which is due to an artifact of the cross section interpolation algorithm for low energy electrons in air, does not affect the results in other materials.
背景
PRIMO 是一种基于通用蒙特卡罗辐射输运代码 PENEL- OPE 的剂量验证系统，它实现了相互作用截面和辐射输运过程的精确物理模型，但与快速蒙特卡罗代码相比计算效率较低。这些快速蒙特卡罗代码之一是剂量规划方法（DPM）。本工作的目的是描述将 DPM 作为 PRIMO 替代计算引擎的改编，以验证其相对于 PENEL- OPE 的性能，并对一些特定情况进行验证。
方法
DPM 被并行化和修改，以在二次几何形状中进行辐射输运，这些几何形状用于描述直线加速器，从而允许对动态治疗进行模拟。为了在准确性和模拟时间方面对新代码与 PENEL- OPE 进行基准测试，进行了多次测试，即对多层模体进行照射，使用多叶准直器（MLC）定义的准直图案对水模体进行照射，以及四个临床病例。使用 1mm/1%的伽马指数来比较吸收剂量分布。使用 3-D 伽马分析比较临床病例。
结果
除了穿过空气的情况外，对于体模情况，通过伽马标准的体素百分比始终超过 99%，而在 DPM 和 PENEL- OPE 之间的剂量差异最大可达 24%。对于临床病例，相应的百分比大于 99%。DPM 和 PENEL- OPE 之间的加速因子范围从 2.5×，用于模拟 MLC 中的辐射输运和随后在水模体中的剂量估算，到用于肺部治疗的 11.8×。当使用体素尺寸为（2.5mm）时，在临床病例中可以获得高达 25×的进一步计算速度提高。
结论
DPM 已被纳入 PRIMO 中的高效准确的蒙特卡罗剂量估算引擎。它允许在静态和动态治疗中，串联模拟直线加速器和患者几何形状中依赖于患者的部分。DPM 和 PENEL- OPE 之间的差异是由于空气低能电子的截面插值算法的一个人为因素引起的，但不影响其他材料的结果。
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