Integrated modality imaging with PET-CT and SPECT-CT: CT issues

Abstract

The advantages of combining PET with CT are multiple and due to the anatomic referencing and the attenuation correction capabilities, which CT introduces, as well as a resulting increase in imaging speed and more efficient use of radiopharmaceuticals. These synergistic advantages are gained with combining PET-CT, but less so when combining SPECT-CT and almost not at all, when combining PET or SPECT with MR. PET-CT in oncology has firmly established itself as the best imaging modality in many settings of tumor staging and therapy monitoring. Whether the CT used in the combined imaging approach should be a full scale contrast enhanced CT or a low mAs unenhanced scan is currently a matter of debate. The use of contrast enhanced CT in PET-CT should be guided primarily by the availability of a prior recent enhanced CT-only scan and the diagnostic questions to be answered by the PET-CT examination and not by turf issues between nuclear physicians and radiologists. The future of combined imaging seems bright, as applications in SPECT-CT and in other disease entities are emerging.