AN EVALUATION OF FDG-PET IN THE DETECTION AND DIFFERENTIATION OF THYROID-TUMORS

We evaluated the usefulness of FDG-PET for the detection of thyroid tu mours and the differentiation between benign and malignant tumours. Th e subjects consisted of 5 normal volunteers and 22 patients, including 3 with follicular adenoma, 16 with papillary carcinoma and 3 with fol licular carcinoma. The results were then evaluated both visually and s emi-quantitatively using the standardized uptake value (SUV). All 22 t umours were seen as areas of high FDG uptake. FDG uptake in the normal thyroid gland, follicular adenoma, papillary carcinoma and follicular carcinoma was 1.0 +/- 0.2, 2.1 +/- 0.4, 4.7 +/- 3.2 and 4.6 +/- 2.9, respectively. Significant differences were observed between papillary carcinoma and both follicular adenoma (P < 0.05) and the normal thyroi d gland (P < 0.001), and between follicular adenoma and the normal thy roid gland (P < 0.001). For the diagnosis of carcinoma, 58% sensitivit y, 100% specificity and 73% accuracy were obtained when the highest FD G uptake value in adenoma was taken as the threshold. Our results thus indicate that high FDG uptake in a thyroid tumour suggests malignancy even though low levels of FDG uptake cannot completely rule out malig nancy.