Biological effectiveness of heavy particle beams

This study is to describe the procedure and logic used to start clinical trials with heavy particle beams at NIRS. We have accumulated our knowledge of fast neutrons and protons produced by NIRS cyclotron in physical, biological and clinical aspects for more than 20 years. Past 5 years, research on heavy particle beams has also been extensively conducted by our group using RIKEN ring cyclotron. Comparing biological effectiveness of 12C beams with that of neutrons, we estimated physical dose of 12C beams suitable for clinical trial. As conclusions, a carbon dose of 1.13 Gy at middle SOBP was recommended as a fraction size in clinical trial which planned to use 3 fractions per week for 6 weeks. (J.P.N.)