Is it practical and cost effective to detect differentiated thyroid carcinoma metastases by (18)F-FDG PET/CT, by (18)F-FDG SPET/CT or by (131)I SPET/CT?

Fluorine-18-labeled 2-fluoro-2-deoxy-D-glucose positron emission tomography/computerized tomography ((18)F-FDG PET/CT) plays an important role in detecting differentiated thyroid carcinoma (DTC) metastases with elevated thyroglobulin (Tg) and negative radioiodine ((131)I) uptake. In conclusion, (18)F-FDG PET/CT may fail to detect all DTC metastases, while (131)I WBS combined with (131)I SPET/CT may be a better cheaper and diagnostic tool as suggested by the case we presented here. Positive metastases in both (131)I and (18)F-FDG SPET/CT may indicate worse prognosis. Future research may add more evidence as to which is the best diagnostic imaging modality and relate it to the molecular mechanism of the uptake of the radionuclide used.