[Objective for clinical use of particle radiations with high LET]

Radiation therapy has made a steady progress in local control of cancer following introduction of megavoltage radiations. Nevertheless, the fact that the doses delivered to the target volume are strongly dependent on the radiation tolerance of the surrounding normal tissues still remains a critical problem. Particle radiations have offered an impact in radiation therapy to improve further local control of cancer. Clinical experiences performed with fast neutrons and protons indicate that the features of high LET radiations will be realized by use of radiations with excellent dose distributions. Heavy ions characterized by Bragg peak with high LET will be introduced with an emphasis to confirm the doses delivered to the target volume.