Li Qiang, Furusawa Yoshiya, Kanazawa Mitsutaka, Kanai Tatsuaki, Kitagawa Atsushi, Aoki Mizuho, Urakabe Eriko, Tomitani Takehiro, Sato Shinji, Yoshimoto Mitsuo, Wei Zengquan
Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China.
Int J Radiat Oncol Biol Phys. 2005 Nov 15;63(4):1237-44. doi: 10.1016/j.ijrobp.2005.08.006.
To evaluate the potential importance of radioactive 9C-ion beam in cancer radiotherapy.
Human salivary gland (HSG) cells were exposed to a double-radiation-source 9C beam at different depths around the Bragg peak. Cell survival fraction was determined by standard clonogenic assay. For comparison, the same experiment was conducted for a therapeutic 12C beam. To determine relative biologic effectiveness (RBE) values, HSG cells were also irradiated with 60Co gamma-rays of fractionation scheme as the reference.
The 9C beam was more efficient in cell killing at the depths around its Bragg peak than was the 12C beam, which corresponded to the 9C-ion stopping region and where delayed low-energy particles were emitted. The RBE value at 50% survival level for the 9C beam varied from 1.38 to 4.23. Compared with the 12C beam, the RBE values for the 9C beam were always higher; an increase in RBE by a factor of up to 1.87 has been observed at the depths distal to the Bragg peak.
The potential advantage of radioactive 9C-ion beam in cancer therapy has been revealed at low dose rate in comparison with a therapeutic 12C beam. This observation, however, remains to be investigated at therapeutic dose rates in the future.
评估放射性碳离子束在癌症放射治疗中的潜在重要性。
将人唾液腺（HSG）细胞置于布拉格峰周围不同深度处的双辐射源碳离子束下。通过标准克隆形成试验测定细胞存活分数。为作比较，对治疗用碳离子束进行了相同实验。为确定相对生物效应（RBE）值，还对HSG细胞进行了分次照射方案的钴-60γ射线照射作为参照。
在布拉格峰周围深度处，碳离子束在杀伤细胞方面比碳离子束更有效，这与碳离子的阻止区域相对应，且该区域会发射延迟的低能粒子。碳离子束在50%存活水平时的RBE值在1.38至4.23之间变化。与碳离子束相比，碳离子束的RBE值始终更高；在布拉格峰远端深度处，观察到RBE值增加了高达1.87倍。
与治疗用碳离子束相比，已揭示出放射性碳离子束在低剂量率癌症治疗中的潜在优势。然而，这一观察结果仍有待于未来在治疗剂量率下进行研究。
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