[Radiation therapy and medical imaging].

The goal of radiation therapy is to deliver a high-dose of radiation to the tumour or target region to improve local control of disease and a low-dose to normal soft tissues to limit side effects. Conformal radiation therapy, intensity modulated radiotherapy (IMRT), brachytherapy and stereotactic radiosurgery have been developed to achieve the desired dose distribution. They require precise imaging of internal anatomy so that it is well adapted to the tumour and organs at risk. Indeed, morphological imaging such as computed tomography is already recommended for radiotherapy planning. But radiation oncologists are also considering other imaging modalities for treatment planning and imaging tools capable of controlling patient motion during treatment. The aim of this article is to present and illustrate the place of imaging during treatment planning and delivery via techniques such as: 4D computed tomography, morphological and functional MRI, positron emission tomography, and imaging devices mounted on accelerators.