CEACAM5 and medullary thyroid gland carcinoma: In this study, we investigated the usefulness of [18F]F-DOPA PET/CT in 109 patients with MTC for the following purposes: (1) the diagnostic value of [18F]F-DOPA PET/CT in patients with MTC; (2) the prognostic value of [18F]F-DOPA PET/CT in patients with MTC; (3) the correlation of Ct and CEA levels with [18F]F-DOPA PET/CT results and exploration of the best thresholds of Ct and CEA for imaging MTC with [18F]F-DOPA PET/CT; and finally (4) the prognostic value of [18F]F-DOPA PET/CT parameters in patients with MTC.