Abstract
Particle beams have a characteristic called the Bragg peak, which is a peak formed at a fixed depth in the body depending on the acceleration energy. Utilizing this property, a high dose can be concentrated in the target tumor while minimizing damage to surrounding normal tissues.
Proton and carbon ion beams have a higher LET than X-rays. The relative biological effectiveness of proton and carbon ion beams compared with X-rays ( = 1) is estimated to be 1.1 and 3.0, respectively. Therefore, we can expect particle radiotherapy to be effective for patients with radio-resistant tumors such as malignant melanoma, adenoidcystic carcinoma and adenocarcinoma.
As of the end of July 2011, there were 9 particle institutes operating in Japan; the Hyogo Ion Beam Medical Center was established in May 2001 as a leading project of the “Hyogo Cancer Strategy”. One major characteristic is that the Center can generate both proton and carbon ion beams. Locally advanced nasal, paranasal or salivary gland cell tumors are good candidates for particle radiotherapy. Downsizing of the accelerator, price reduction of the machine, broad use of particle therapy in the field of clinical oncology, and intensity modulated particle therapy are future challenges.
