1. An apparatus for combined magnetic resonance tomography and positron emission tomography imaging, designed to record PET image data of a person under examination from an examination area, comprising: a scanning unit, embodied to scan a prespecified area of the person under examination and based on the scanning, to determine a contour of the person under examination for the prespecified area; and a processing unit, embodied to carry out an absorption correction of PET data which were previously recorded from the prespecified area of the person under examination, based on the contour determined.