A combined tomography scanner is disclosed, having at least two imaging modalities. In at least one embodiment, the scanner includes a first tomography modality having an essentially annular or tubular measurement area opening formed by an inner perimeter; an annular or cylindrical PET component as a second tomography modality having an outer perimeter, which allows insertion into the measurement area opening, and having an inner opening which forms a patient tunnel; and at least one insulation mat which can be inserted into an annular gap between the inner perimeter of the first modality and the outer perimeter of the PET component.