The study will consist of 2 successive steps:~Step 1 : for a set of patients selected in the clinical centers participating in the study, 3D maps of physical doses delivered to organs by positioning imaging will be calculated based on the patient's CT image used by the treatment planning system (dosimetric calculation performed by Monte Carlo method).~Step 2/ all the new dosimetric data, average organ doses and dose volume histogram, will be the subject of a more global analysis, which will be returned to the project's clinical partner centers.
In image-guided radiotherapy (IGRT), the repeated and increasingly intensive use of on-board positioning imaging, using 2D or 3D Mega-Volt (MV) or kilo-Volt (kV) imaging devices (cone-beam or CBCT scanners), is leading the international medical community to question the potential impact of these additional doses delivered to the patient, especially in at-risk populations such as children and young adults. The doses delivered to the patient by positioning imaging are still relatively unknown, due to the lack of experimental means and software available in clinical routine to easily and accurately evaluate these doses.~The main objective is to estimate by personalized Monte Carlo calculation the physical doses delivered to the patient's organs by the onboard imaging systems during their radiotherapy treatment. The obtained imaging doses will be compared according to different irradiation scenarios commonly used in clinical routine as well as according to the treated location.