Method to register multiple different imaging modalities warming an examination subject in a common image acquisition region of all imaging modalities, simultaneous or time-offset acquisition of at least one first image data set with a first imaging modality, simultaneous or time-offset acquisition of at least one second heat image data set with a second imaging modality, determining at least one item of heat information resulting from the warming of the examination subject is determined from each of the first image data set and the second heat image data set, and registration of the imaging modalities using the determined heat information.