Added value of early 18F-FDOPA PET/CT acquisition time in medullary thyroid cancer.

The aim of this study was to determine whether early acquisition of F-fluorodihydroxyphenylalanine (F-FDOPA) PET/CT could improve the detection of medullary thyroid cancer (MTC). We retrospectively compared early (median time: 15 min) and delayed (median time: 94 min) acquisitions, positive on at least one of the two phases, in 15 dual-phase F-FDOPA PET/CT examinations performed on 14 patients referred for initial staging (one examination), suspected recurrence (eight examinations) or restaging of MTC (six examinations). Among the 14 true-positive (TP) examinations, more lesions (51 vs. 43) or more intense uptake (mean SUVmax=4 vs. 2.4, P<0.05) was observed on early versus delayed phases, regardless of the anatomical site of disease (lymph node, liver or bone). The only false-positive case, a reactive lymph node, was visible only on the delayed acquisition. Early acquisition appeared to be more appropriate in the detection of MTC lesions compared with acquisition at 60 min or later.