Positioning quality control of radiotherapy Method

The invention relates to a method of determining an efficiency of a movement performed on a patient in a radiation therapy, a method implemented by a data processing device from at least one image of treatment planning and at least one follow-up treatment picture. According to the invention such a method comprises: - a stage of obtaining at least a position of a tumor structure within said tracking image; - a first phase for calculating a displacement of said tumor structure, providing at least data representative of a realized repositioning; a second phase for calculating data representative of an optimal repositioning; - a comparison of phase of said at least one datum representative of a realized and repositioning said at least one datum representative of an optimal repositioning, delivering at least one displacement efficiency indicator.