The relationship between penetration depth of X-rays and heavyions in water and corresponding cell survival fraction， with Hela and B16 cells， were studied， respectively. The results showed there were significantly different variation rules for X-rays and heavy ions in correlation between depth and cell survival. The relationship between depth and survival fraction for X-rays displayed highly positive correlation， i. e. r=0.92. However， heavy ions had less damage effect on cells and existed a plateau region with 80%—92% survival fraction following passing through the cells; while at the end of their range, cells were greatly damaged and their survival fraction decreased dramatically， presenting an inverse Bragg peak. It is suggested that tumor therapy with heavy ions have a better curing efficiency compared to X-rays.%采用Hela、B16两种细胞分别研究了X射线和重离子在水介质中入射的深度与相应细胞的存活率(1-失活率)。结果表明:X射线与重离子在入射深度与细胞存活关系上有明显不同的变化规律。X射线的入射深度与其细胞存活率呈高度正相关性,r=0.92;而重离子通过路径的细胞损伤率较小、且有一个细胞存活较高的坪区(86%—92%),到射程末端细胞损伤率剧增,出现倒Bragg峰。提示:重离子在深层肿瘤治疗上具有比X射线好的深度治疗分布。
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