Computation of cell survival in heavy ion beams for therapy - The model and its approximation
Computation of cell survival in heavy ion beams for therapy - The model and its approximation
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DOI：
10.1007/s004110050055
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发表时间：
1997-02-01
影响因子：
1.7
通讯作者：
Kraft, G
中科院分区：
文献类型：
--
作者：
Scholz, M;Kellerer, AM;Kraft, G
基于 Scholz 和 Kraft 的轨道结构模型，提出了一种计算带电粒子照射后哺乳动物细胞存活率的简化方法 [1, 2]。利用 X 射线生存曲线的修正线性二次关系，我们发现该模型对于重离子照射也产生线性二次关系。如果将存活率计算为细胞核中特定能量 z 的函数，从而减少能量沉积的随机波动，则存活曲线斜率的增加，因此可以根据初始斜率 alpha(z) 以足够的精度估计系数 beta(z)。这允许将感兴趣的粒子类型和能量的系数 alpha(z) 制成表格，并随后快速计算混合粒子束中任意点的生存水平。因此，在广泛的应用中可以降低计算的复杂性，这使得重离子治疗中的治疗计划所需的快速计算成为可能。通过与原始模型的显式计算以及轨道段条件的实验结果进行比较来评估修改计算的有效性。然后使用该模型分析束碎裂对带电粒子束穿透组织不同深度的生物效应的影响。此外，中子照射后的细胞存活率是根据二次带电粒子的减速光谱计算出来的，并与实验观察结果进行比较。
A simplified method for the calculation of mammalian cell survival after charged particle irradiation is presented that is based on the track structure model of Scholz and Kraft [1, 2]. Utilizing a modified linear-quadratic relation for the x-ray survival curve, one finds that the model yields linear-quadratic relations also for heavy ion irradiation. If survival is calculated as a function of specific energy, z, in the cell nucleus - thus reducing the stochastic fluctuations of energy deposition - the increase in slope of the survival curve and therefore the coefficient beta(z) can be estimated with sufficient accuracy from the initial slope, alpha(z). This permits the tabulation of the coefficients alpha(z) for the particle types and energies of interest, and subsequent fast calculations of survival levels at any point in a mixed particle beam. The complexity of the calculations can thereby be reduced in a wide range of applications, which permits the rapid calculations that are required for treatment planning in heavy ion therapy. The validity of the modified computations is assessed by the comparison with explicit calculations in terms of the original model and with experimental results for track-segment conditions. The model is then used to analyze the influence of beam fragmentation on the biological effect of charged par tide beams penetrating to different depths in tissue. In addition, cell-survival rates after neutron irradiation are computed from the slowing-down spectra of secondary charged particles and are compared to experimental observations.