ABSTRACT
Heavy-ion beams have drawn growing interest for their use in cancer treatment not only due to their high dose localization at the Bragg peak, but also due to the high biological effect in this region. In 1946, R.R. Wilson proposed the clinical applications of protons and heavier ions in the treatment of human cancer (Wilson, 1946). Pioneering work on clinical applications of proton and helium beams was carried out (Tobias et al., 1952) using the 184 in. synchrocyclotron at the Lawrence Berkeley National Laboratory (LBNL). More than 1000 patients had been treated since 1957. Between 1977 and 1992, 433 patients were treated with heavy-ion beams accelerated by the Bevalac (Alonso, 1993). Encouraged by the prospective results of heavy-ion radiotherapy at LBNL and the recent progresses in the accelerator and beam-delivery technologies (Chu et al., 1993), the National Institute of Radiological Sciences (NIRS) decided to carry out heavy-ion radiotherapy. The construction project of the Heavy-Ion Medical Accelerator in Chiba (HIMAC) (Hirao et al., 1992) was promoted by NIRS as one of the projects of “Comprehensive 10-year strategy for cancer control” that was initiated by the Japanese government in 1984. The construction of the HIMAC facility was completed in 1993, and it was the Ÿrst heavy-ion medical accelerator facility dedicated to cancer radiotherapy in the world. On June 21, 1994, NIRS began heavy-ion radiotherapy using carbon-ion beams generated by the HIMAC accelerator complex. Since then, clinical studies to develop safe and secure irradiation technologies and optimized dose fractionation for various diseases have been conducted. More than 4500 patients have been treated with HIMAC at NIRS, and the clinical efŸcacy of carbon-ion radiotherapy has been demonstrated for various diseases.
