Physical basis of heavy ion radiation therapy

Physical foundation of a heavy ion radio-therapy was discussed, especially on a designing a spread Bragg peak with a ridge filter. A large radiobiological effectiveness will be positively utilized in the heavy ion radio-therapy. The biological effectiveness will be different depending on the depth in human body. This fact gives us difficult problems when we aim to kill uniformly the target cells in human body. As a first step to solve these problems, biological effectiveness of a mixed beam using monoenergetic low and high LET beams was examined and try to understand the results by the amorphous image of the track structure of the heavy ions. A research on a microscopic pattern of energy deposition will be important to solve biophysical problem in heavy ion radio-therapy. (author)