Development of imaging modality and radiotherapy

The modality of radiotherapy has changed from 2D to 3D mode and this paper describes the present state and future aspect of the highly accurate radiotherapy (HART), which is essentially guided by imaging techniques for diagnosis. HART consists of the decision of radiation target, HART planning and actual practice of HART. For deciding the target, CT imaging is essential and multi-detector CT, dynamic enhanced CT, CT endoscopy and MR spectroscopy are recent important advances. Many computing methods are now introduced for the HART planning from the re-constructed images like beam's and room's eye views. In actual irradiation, stereotactic body and intensity modulated radio-therapeutic techniques are recent advances in HART. The former, originally for the brain tumors with the irradiation field accuracy of <1-2 mm, is widely applied to cancers of lung and liver, and spinal arteriovenous anomaly on the national health insurance system. The latter is on the computer-controlled therapy to optimize the 3D dose distribution in the target and is applied to cancers of prostate, head/neck, brain and breast. Progress of HART is toward 4D therapy. (S.I.)