[Intensity-modulated radiation therapy (IMRT)].

Intensity-modulated radiation therapy (IMRT) is a new type of conformal radiotherapy which is based on the use of non-uniform radiation beam intensities, optimized by inverse planning. IMRT can achieve the optimal dose distributions and may improve the clinical outcomes dramatically. However, it is not easy to deliver IMRT properly because of its complexity. If IMRT is used inadequately, the outcome might be worse than conventional therapies. This is why the clinical and physical quality assurance (QA) should be done strictly to deliver IMRT. The clinical use of IMRT is permitted only for prostate cancers, head and neck cancers and brain tumors as health insurance treatments in Japan. IMRT is available in only about 50 institutions for now in Japan.