The aim of this study was to evaluate the usefulness of 18-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) and technetium-99m tetrofosmin (Tc-99m TF) single photon emission computed tomography (SPECT) to detect metastatic neck lymph nodes. (LN) in papillary thyroid carcinoma (PTC) after total thyroidectomy and radioiodine-131 (I-131) treatments in patients with elevated serum human thyroglobulin (hTg) levels but negative I-131 whole body scan (WBS). Thirteen PTC patients underwent nearly total thyroidectomy and I-131 treatments with proven neck LN metastases were included in this study. All subjects had negative I-131 WBS and elevated hTg levels (hTggreater than or equal to10 muIU/ml) under thyroid-stimulating hormone (TSH) stimulation (TSHgreater than or equal to30 muIU/ml). FDG-PET and Tc-99m TF SPECT were used to detect metastatic neck LN in PTC. FDG-PET could detect all of the 13 (100%) patients with metastatic neck LN, but Tc-99m TF SPECT revealed lesions in only 8 out of 13 (61.5%) patients (p<0.05). This study demonstrated that FDG-PET is more sensitive than Tc-99m TF SPECT to detecting metastatic neck LN in PTC with elevated serum hTg levels but negative I-131 WBS.
