Development of Simulation System for Radiotherapy Effect utilizing Complexity

我们从两个方面探讨了放疗中放疗对肿瘤缩小的影响。首先，我们假设肿瘤是由相互作用的细胞组成的复杂性，利用二维元胞自动机模型模拟肿瘤在放疗过程中形状的变化。其中一名合作研究者，Ouchi A，已经尝试使用一种自动机模型，利用体内研究得出的参数，通过免疫反应来缩小肿瘤。免疫治疗模型的建立表明，为了将自动机模型应用于辐射反应，我们需要更多关于参数的可靠信息。另一方面，我们假设肿瘤是一种可变形的物质，它的大小与辐射剂量有关。我们将应力-应变关系应用于基于细胞死亡线性二次模型的剂量-反应关系。随着宫颈肿瘤放疗后肿瘤体积的变化，该方法取得了较好的效果。将仿真模型集成到自适应放疗中是四维调强放疗的重要步骤。随着分子成像技术的发展，更多的可靠信息有待实现。

We have investigated from two aspects about the radiation effect on the tumor shrinkage in radiotherapy. First, we assumed that the tumor is complexity consisted of cells which are interacting each other and to simulate the change of shape of tumor by the radiotherapy using two-dimensional cellular automaton model. One of the co-investigator, Ouchi A, has tried to use an automaton model for the shrinkage of the tumor by immuno-response using the parameters derived from in vivo studies. The modeling of the immunotherapy suggested that we need more solid information about the parameters for the application of the automaton model to the radiation reaction. On the other hand, we assumed that the tumor is a deformable material decreases it size in relation to the radiation dose. We applied stress-strain relationship to the dose-response relationship based on the linear-quadratic model for cell deaths. This approach has succeeded reasonably well with the change of tumor volume after radiotherapy for uterine cervix tumors. Integration of the simulation model in the adaptive radiotherapy will be important step in the four-dimensional intensity-modulated radiotherapy. More solid information is to be implemented in accordance with the achievement in molecular imaging technology.