A user predefines for a computer a retrieval instruction for primary data of a patient or of several patients. The computer accesses the primary data of this patient and outputs them to the user via a visual display device. The primary data comprise the primary image data recorded by way of a primary imaging modality and/or primary information derived from said primary image data. The computer automatically checks whether it is possible to access secondary data of this patient, which comprise the secondary image data recorded via a secondary imaging modality and/or secondary information derived from said secondary image data. In the affirmative case, the computer outputs a corresponding message to the user via the visual display device and/or by accessing at least a portion of the secondary data of this patient and outputting said data to the user via the visual display device.