Control of the dose delivered in external radiotherapy: study of the mutual contribution of on-board volume imaging and transit dosimetry

In external radiation therapy, the treatment is delivered to the patient with a fraction every day using the treatment established before and repeated until the end of the treatment. Treatment planning is establish using anatomical information of the patient and a dose calculation. New technologies already integrated to the treatment units can be used to check the positioning of the patient and anatomical information (Electronic Portal Imaging Device - EPID-, Cone Beam Computed Tomography - CBCT - ). The main goal is to develop a system to control the dose delivered to the patient from the dose establish with the TPS. The first aim of this work is to integrate portal images to compare and assess the position of the patient at each fraction to the planned one (CT images) by accepting, rejecting or ignoring the patient positioning and dose level discrepancy according to a tolerance threshold defined by the user. The second aim is to integrate on board imaging to reconstruct the delivered dose using a dose calculation. Following the dose received by the patient day after day, based on new indicators, it can be established a traceability to identify deviation and assess treatment quality. To conclude, these new indicators would allow a double traceability: in one hand the improvement of the calculation and then the efficiency of the treatment; in another hand the safety of the treatment and the technique used. (author)