2. IGRT background

2.1 Objectives

IGRT is designed to ensure that the dose delivered complies with the planned or desired dose, after adaptation in the light of feedback. Numerous studies have shown that it reduces repositioning uncertainties and can sometimes visualize anatomical or tumor changes, enabling corrections and adaptations to be made. On the other hand, the clinical benefit of IGRT is difficult to demonstrate, as IGRT has been used from the outset to ensure correct irradiation delivery. IGRT is therefore part of a quality assurance (QA) approach.

Theoretically, IGRT would :

• a reduction in safety margins (PTV for planned treatment volume, including geometric uncertainties in patient repositioning on the one hand, and an...