目的：以14 MeV快中子照射体外培养的U251(人脑胶质瘤) 细胞，研究快中子诱发U251的相关生物效应；方法：快中子照射U251细胞，吸收剂量分别为1、3、5、7 Gy，辐照后检测细胞的存活率、凋亡率、生长曲线以及周期变化等相关指标；结果：随着吸收剂量的增加，细胞存活率下降，凋亡率上升，呈良好的剂量-效应关系。照射后24 h，细胞生长曲线无明显变化；照射后48 h，细胞增殖速度明显变缓；结论：快中子为高LET射线，与相关文献报道的γ射线相比，快中子具有较高的相对生物效应。

Objective: U251 cells were exposed to fast neutrons of 14 MeV energy, and dose-response relationships were derived; Methods:cell samples were exposed to fast neutrons. Radiation doses were 1 Gy, 3 Gy, 5 Gy and 7 Gy respectively. The cell survival, apoptotic rate and proliferation were tested after irradiation; Result: with the growth of the radiation dose, cell survival was declined, and apoptotic rate was promoted; the speed of the cell proliferation, which was observed 48 h after irradiation, was slowed down viously; Conclusion: compared to γ ray, fast neutrons have higher relative biological effectiveness.