Biophysical characteristics of HIMAC clinical irradiation system for heavy-ion radiation therapy

Purpose: The irradiation system and biophysical characteristic carbon beams are examined regarding radiation therapy. Methods and Materials: An irradiation system was developed for heavy-ion ra diotherapy. Wobbler magnets and a scatterer were used for flattening the ra diation field. A patient-positioning system using X ray and image intensifi ers was also installed in the irradiation system. The depth-dose distributi ons of the carbon beams were modified to make a spread-out Bragg peak, whic h was designed based on the biophysical characteristics of monoenergetic be ams. A dosimetry system for heavy-ion radiotherapy was established to deliv er heavy-ion doses safely to the patients according to the treatment planni ng. A carbon beam of 80 keV/mu m in the spread-out Bragg peak was found to be equivalent in biological responses to the neutron beam that is produced at cyclotron facility in National Institute Radiological Sciences (NIRS) by bombarding 30-MeV deuteron beam on beryllium target. The fractionation sch edule of the NIRS neutron therapy was adapted for the first clinical trials using carbon beams. Results: Carbon beams, 290, 350, and 400 MeV/u, were used for a clinical tr ial from June of 1994. Over 300 patients have already been treated by this irradiation system by the end of 1997. (C) 1999 Elsevier Science Inc.