When generating a magnetic resonance attenuation map, an MR image is segmented to identify a patient’s body outline, soft tissue structures, and ambiguous structures comprising bone andor air. The paper cutting device enables the spacing between the stationary blade and the first and second movable blades to be opened by moving the stationary blade frame and the movable blade frame relative to each other. The cable channels open at the bottom, into which the drive cables can easily be laid, are closed by at least one likewise plastic injection molded cover element.