1. A computerized device for generating an exposure plan for irradiating a patient, comprising: a computer having access to at least one reference data set representing a reference body that is independent of the patient, said computer determining, from said at least one reference data set, attenuation of penetrating radiation upon passage through said reference body; said computer also having access to magnetic resonance data representing a patient magnetic resonance image of the patient, and said computer comprising an adaptation unit that adapts said patient magnetic resonance image dependent on said reference data set; said computer determining patient-specific attenuation of penetrating radiation upon passage through the patient from the adaptation of the patient magnetic resonance image with the reference data set, and said computer generating an exposure plan dependent on said patient magnetic resonance image and said patient-specific attenuation of penetrating radiation; and an output unit in communication with said computer at which said computer causes said exposure plan to be visually presented.