DETERMINATION OF MALIGNANCY OF THYROID-NODULES WITH POSITRON EMISSIONTOMOGRAPHY

Background. Current noninvasive evaluation techniques of thyroid nodul es are nonspecific. We studied the use of a new noninvasive imaging mo dality, positron emission tomography (PET), in the evaluation of thyro id nodules. Methods. Nineteen patients were studied before operation w ith PET with [F-18]-2-deoxy-2-fluoro-D-glucose (FDG). Twelve patients had solitary thyroid nodules and seven had multinodular goiters. Fourt een overlapping transverse slices were acquired through the thyroid gl and. A region of interest was drawn around the abnormal area and the m aximum pixel value was calculated and corrected to produce a normalize d value for FDG uptake. Results. Four of the 12 nodules were malignant (three papillary and one follicular carcinoma), with the others being follicular adenomas. All of the multinodular goiters were benign. All of the malignancies had an FDG greater than 8.5 and all of the benign nodules had an FDG less than 7.6. The dose uptake ratio of FDG was 10 .8 +/- 3.2 (mean +/- SD) for the malignancies and was significantly gr eater than the dose uptake ratio of either the follicular adenomas (4. 3 +/- 2.0) or the dominant nodule in multinodular goiters (3.0 +/- 2.0 ). Conclusions. The FDG uptake as measured by PET scanning successfull y discriminant between all benign and malignant tumors. This technique appears useful in the evaluation of thyroid nodules.