Studies on advantages of heavy ions in radiotherapy compared with c-rays Guo Chuanling a,b, * , Wang Jufang a , Jin Xiaodong a , Jing Xigang a,b , Li Renmin a,b Wei Wei a,b , Li Wenjian a a Institute of Modern Physics, The Chinese Academy of Sciences, Lanzhou 730000, China b Graduate School of Chinese Academy of Sciences, Beijing 100039, China Received 12 October 2006; received in revised form 6 March 2007 Available online 24 March 2007 Abstract Hepatoma and melanoma cells were exposed to 12 C 6+ beams generated by HIRFL facility and c-rays and the cell response was stud- ied by colony assays as well as the analysis of RBE of carbon ions was evolved. The survival curves of cells irradiated by heavy ions were different from those of cells irradiated by c-rays. And two kinds of cell showed the obvious discrepancy in response to the photon and ion irradiation. The results showed that heavy ions have special physical properties and mighty potency to kill cell in both single and frac- tional irradiation meanwhile it can kill tumor cells with high radioresistance more efficiently. When involved in clinical therapy, heavy ions will enhance the therapy efficiency and decrease the suffering of patients because it can impair the repair for sublethal damage of cells which can lead to fewer irradiation fractions. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Heavy ions; Radiotherapy; Survival fraction; RBE 1. Introduction From last century, scientists from many groups such as the Japanese Research Centre NIRS (Chiba) and the group of Prof. G. Kraft and Dr. M. Scholz at GSI Darmstadt (Germany) hammered at the basic research on radiother- apy with charged ions. First applications of charged parti- cle beams in tumor therapy were all performed at accelerators constructed for fundamental research in nuclear and particle physics. Only in the last decade the first fully hospital based treatment facilities were built in Loma Linda and Chiba and the fact heavy ion therapy is considered to be a promising modality against tumors has been recognized in the community of radiation therapy. Studies of the biological action of ionizing radiation on cells and tissues are of interest in radiotherapy. In general, the biological response to ion beam irradiation consider- ably differs from that to conventional photon beam irradi- ation. The difference, for example, constitutes one of the major rationales for the application of ion beam in tumor therapy and thus heavy charged particle beams such as 12 C 6+ have been applied in tumor therapy because of their clear radiobiological response in the destruction of malig- nant tumor cells [1]. Investigation of radiation induced cell death, defined as mitotic death in the sense of a complete loss of the prolif- eration capacity, is one of the most commonly used meth- ods to study radiation effects. Colony assay is the most pervasive method referring to obtain the cell survival result and the dose–survival curve can directly present the response of cell to irradiation. In addition, the specific bio- logical effects of charged particle radiation were recognized as early as 1935 [2] and the enhanced effectiveness of ion 0168-583X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.03.010 * Corresponding author. Address: Institute of Modern Physics, The Chinese Academy of Sciences, Lanzhou 730000, China. E-mail address: chlguo@impcas.ac.cn (C. Guo). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 259 (2007) 997–1003 NIM B Beam Interactions with Materials & Atoms