Adaptation of stochastic microdosimetric kinetic model for charged-particle therapy treatment planning
Adaptation of stochastic microdosimetric kinetic model for charged-particle therapy treatment planning
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DOI：
10.1088/1361-6560/aabede
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发表时间：
2018-05-01
影响因子：
3.5
通讯作者：
Kanematsu, N.
中科院分区：
文献类型：
--
作者：
Inaniwa, T.;Kanematsu, N.
微剂量动力学（MK）模型低估了高线性能量传递（LET）和高剂量辐照的细胞存活分数。为了解决这个问题，一些研究人员以前扩展的MK模型的随机微剂量动力学（SMK）模型。在SMK模型中，辐射诱导的细胞存活分数分别由微观亚核结构域和细胞核吸收的比能量z（d）和z（n）估计。通过考虑z（n）和z（d）的随机性，SMK模型可以再现宽LET和剂量范围辐射下的细胞存活率。然而，基于SMK模型的治疗计划在临床实践中是不现实的，因为其计算时间长，计算所需的存储空间巨大。在这项研究中，我们修改了SMK模型，以缩短计算时间，减少计算所需的内存空间。通过使用SMK形式体系中的每事件的剂量平均细胞核比能（z）超过棒（n），D，z（n）的随机性质反映在估计的细胞存活分数上。通过比较人涎腺肿瘤细胞和V79细胞的存活分数的估计值和测量值，检验了改进的SMK模型的准确性。然后，我们将修改后的SMK模型应用到扫描带电粒子治疗的内部治疗计划软件中，以验证其在临床实践中的适用性。作为例子，氦-，碳-和氦-离子束的治疗计划，为一个轨道肿瘤的情况下。与MK模型相比，改进的SMK模型可以更准确地再现测量的细胞存活分数，特别是对于高LET和高剂量辐照。总之，修改后的SMK模型提供了广泛的LET和剂量范围的扫描带电粒子治疗的治疗计划所需的准确性和简单性。
The microdosimetric kinetic (MK) model underestimates the cell-survival fractions for high linear energy transfer (LET) and high dose irradiations. To address the issue, some researchers previously extended the MK model to the stochastic microdosimetric kinetic (SMK) model. In the SMK model, the radiation induced cell-survival fractions were estimated from the specific energies z(d) and z(n) absorbed by a microscopic subnuclear structure domain and a cell nucleus, respectively. By taking the stochastic nature of z(n) as well as that of z(d) into account, the SMK model could reproduce the measured cell-survival fractions for radiations with wide LET and dose ranges. However, treatment planning based on the SMK model was unrealistic in clinical practice due to its long computation time and huge memory space required for the computation. In this study, we modified the SMK model to shorten the computation time and to reduce the memory space required for the computation. By using the dose-averaged cell-nucleus specific energy per event (z)over-bar(n), D in the SMK formalism, the stochastic nature of z(n) was reflected onto the estimated cell-survival fractions. The accuracy of the modified SMK model was examined through the comparison between the estimated and the measured survival fractions of human salivary gland tumor cells and V79 cells. We then implemented the modified SMK model into the in-house treatment planning software for scanned charged-particle therapy to validate its applicability in clinical practice. As examples, treatment plans of helium-, carbon-, and neon-ion beams were made for an orbital tumor case. The modified SMK model could reproduce the measured cell-survival fractions more accurately compared to the MK model especially for high-LET and high-dose irradiations. In summary, the modified SMK model offers the accuracy and simplicity required in treatment planning of scanned charged-particle therapy for wide LET and dose ranges.