[In room delivered doses during image-guided radiotherapy courses]

Image-guided radiotherapy is defined by the use of images acquired in the treatment room to improve the accuracy of patient positioning. Most of imaging devices use X-rays and deliver an additional dose to the patients. These non-negligible doses have to be evaluated and reported. Several studies have investigated organ-absorbed dose due to in-room imaging. Some organ doses are reported to give an idea of the magnitude, in particular for prostate cancer. Then, principles based on the as low as reasonably achievable (ALARA) concept are described and adapted to image-guided radiotherapy. Justification (what is the patient outcome?) and optimisation (image modality, acquisition frequency, treatment site...) are two main issues. They have a really big impact on patient treatment and staff organization.