1. A method for monitoring a radiation dose applied to a patient being exposed or having been exposed to radiation of a medical imaging system, the medical imaging system comprising an X-ray source, the X-ray source describing a trajectory in a coordinate system of reference of the medical imaging system having an origin, the method comprising: determining current coordinates in the coordinate system of reference of the medical imaging system of a current region currently exposed or having been exposed to radiation of the X-ray source, of an envelope of a patient model, in relation to a current position of the X-ray source; determining, from the current coordinates, a current coordinate system of reference having as an origin the current position of the X-ray source, the current coordinate system of reference being centered on the current region; and displaying a representation of the current region centered on the current coordinate system of reference.