以電腦演算法估計二甲基亞碸（DMSO） 用於放射治療之影響

Computational evaluation of biological effects of dimthylsuphoxide for radiotherapy

Studies show that dimthylsulphoxide (DMSO) is a radical scavenger that can protect cells against radiation such as γ-rays and helium partic1es. This study used computational methods to evaluate the biological effects, i.e. cell survival under different concentrations of DMSO for cells exposed to various types of radiation. The repair-misrepair-fixation (RMF) model has been shown to better connect the DNA double strand break (DSB) formation and cell survival. We used Monte Carlo Damage Simulation code to computationally obtain DSB for cells exposed to γ-rays and helium partic1es and regression analysis of experimental survival data to determine other parameters in the RMF model. We then calculated the radiosensitivity parametersαand ß of the linear-quadratic (LQ) model formulated by the RMF model to obtain survival curves. The model-derived survival curves generally agreed well with the experimental results. The analysis in radiosensitivity parameters αand ß of LQ model for 60Co and helium partic1es suggests that radioprotection by DMSO increases dramatically at DMSO concentration 0-0.2 M but more slowly when the concentration is over a specific point such as 0.5 M. The proposed algorithm can also be used for the estimation of radioprotection by DMSO for other types of radiation such as carbon ions and neon ions for radiotherapy. 研究報告指出在細胞受到輻射線傷害時，二甲基亞碸(DMSO) 可有效保護細胞，因此也被應用於各式的放射治療。本篇主要是以電腦演算法估計二甲基亞碸對受到輻射線損傷的細胞的保護作用，以俾用於放射治療時之參考。RMF模型已建立出DNA雙股斷裂和細胞存活率的關係。根據RMF模型，利用非線性迴歸法從實驗數據得出RMF model中所須之參數，並以此參數和隨著DMSO濃度改變而改變的DNA雙股斷裂量，可計算出線性平方模型(LQ model) 的參數α和β，從而得出細胞存活率之理論值。首先我們驗證在60Co和氦離子照射下，電腦模擬得出之DNA雙股斷裂量和實驗結果近似。進一步，我們藉由RMF model和LQ model得出細胞存活率的理論值並和實驗的細胞存活率相比較，顯示在X光及60Co和氦離子的照射下，理論值和實驗結果近似。參數α和β的分析結果也顯示，在DMSO濃度0-0.2M之間的輻射線保護會急遞上升，但到0.5M附近則趨緩。在60CO和氦離子輻射的分析中，都顯示這種和DMSO濃度有關的保護效應。這個方法也可用於計算DMSO對其他離子如碳離子和氖離子輻射的保護作用。