This radiotherapy utilizes heavy ion (carbon ion) beams.
In the field of radiation oncology, heavy ion beams are defined as radiation that is obtained by accelerating charged nuclei heavier than protons. Among various types of ion beams, carbon ion beams in particular are used for cancer therapy, because they are considered to have the most balanced, ideal properties due to their potential ability of selective irradiation and intensive killing effects on cancers.
Heavy ions accelerated to 70% of light speed are delivered to cancer.
In heavy ion radiotherapy, heavy ions (carbon ions) accelerated to approximately 70% of light speed are used to attack cancers deep in the body. In conventional X-ray radiotherapy, the radiation dose decreases as the depth of penetration in the body increases. In heavy ion radiotherapy, however, the radiation dose increases with depth to produce a peak (called a Bragg peak) in a finite depth of the body, enabling selective irradiation of cancers. In addition, the cell killing effect of heavy ions increases with depth, reaching the maximum at the peak region.
The target (cancer) can be externally irradiated with heavy ion beams, corresponding to any irregular shape of the target.
In heavy ion radiotherapy, a sufficient dose can be concentrated on the lesion, with the peak conforming to its shape and position (depth). In order to deliver ion beams precisely to any irregular lesion shape, individually specialized instruments, called a collimator and a compensating filter, are used.
Heavy ion irradiation is individualized, making it possible to minimize the unnecessary dose to the critical organs such as the spinal cord, brain stem and intestines.