Fast Neutron Ray Radiation Biology Research And Its Application In Soft Tissue Sarcoma Radiotherapy

PART 1Objective: To determine the cell killing effects and relative biologicaleffectiveness(RBE) on two human tumor cell lines by 35MeV p→Be fast neutron and 6MV-X ray, and to analyze the influencing factors.Material and methods: Exponentially growing human nasopharyngeal cancer cell line CNE-1 and human fibrosarcoma cell line HT1080 were irradiated in vitro with 35MeV p→Be fast neutron and 6MV-X ray in grading doses(0ncGy, 40ncGy, 80ncGy, 120ncGy, 160ncGy, 240ncGy, 320ncGy, 400ncGy for neutron and OcGy, lOOcGy, 200cGy, 300cGy, 400cGy, 600cGy, 800cGy, lOOOcGy for X ray). Then the clonogenic assay was performed, and RBE was determined with SF₂, Do, Dq, N and D₁₀ by means of cell survival curves. Results: The cell rates for fast neutron were much lower than that of X ray inequal doses. Cell survival curves derived after X ray irradiation exhibited a 'shoulder' portion in the low dose region, Cell survival curves for fast neutron were more like straight lines. The difference of the cell survival rates between the two cell lines was smaller after neutron irradiation than that after X ray irradiation. The RBE of fast neutron to X ray in CNE-1 and HT-1080 cells according to the ratio of D₁₀, which stands for a middle intensity of cell killing, were 2.40 and 1.87 respectively.Conclusions: Fast neutron can kill the tumor cells more effectively than X ray. Tumor cell lines with different radiosensitivity to X ray showed close sensitivity to fast neutron. The RBE of fast neutron to photon can vary significantly with different endpoints.PART 2Objective: To study the radiobiological effects of the mixed beam of fast neutron...