Recent innovations in carbon-ion radiotherapy.

In the last few years, hospital-based facilities for carbon-ion radiotherapy are being constructed and proposed in Europe and Asia. During the next few years, several new facilities will be opened for carbon-ion radiotherapy in the world. These facilities in operation or under construction are categorized in two types by the beam shaping method used. One is the passive beam shaping method that is mainly improved and systematized for routine clinical use at HIMAC, Japan. The other method is active beam shaping which is also known as beam scanning adopted at GSI/HIT, Germany. In this paper an overview of some technical aspects for beam shaping is reported. The technique of passive beam shaping is established for stable clinical application and has clinical result of over 4000 patients in HIMAC. In contrast, clinical experience of active beam shaping is about 400 patients, and there is no clinical experience to respiratory moving target. A great advantage of the active beam shaping method is patient-specific collimator-less and compensator-less treatment. This may be an interesting potential for adaptive radiotherapy.