Determination of malignancy of thyroid nodules with positron emission tomography

Current noninvasive evaluation techniques of thyroid nodules are nonspecific. We studied the use of a new noninvasive imaging modality, positron emission tomography (PET), in the evaluation of thyroid nodules.

Nineteen patients were studied before operation with PET with [18F]-2-deoxy-2-fluoro-D-glucose (FDG). Twelve patients had solitary thyroid nodules and seven had multinodular goiters. Fourteen overlapping transverse slices were acquired through the thyroid gland. A region of interest was drawn around the abnormal area and the maximum pixel value was calculated and corrected to produce a normalized value for FDG uptake.

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 greater 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).

The FDG uptake as measured by PET scanning successfully discriminated between all benign and malignant tumors. This technique appears useful in the evaluation of thyroid nodules.