Whole body Positron Emission Tomography (PET) was used to evaluate the existence of cancer cells. However, PET had limitations in identifying thyroid cancer cells because of their slow progression, and evidence regarding its accuracy in finding thyroid cancer cells is insufficient. Therefore, we investigated the usefulness of PET for evaluation of patients with thyroid nodules by studying the relationships between PET and thyroid ultrasonography.

We evaluated 4,627 patients who had undergone PET from January 2007 to October 2011 and selected 370 patients who had undergone thyroid ultrasonography. We compared and analyzed the amount of thyroid SUVmax of PET, the pattern of glucose uptake, and findings of thyroid ultrasonography based on their size, shape, location, and FNAC.

Of 370 patients, 197 (53.2%) subjects were found to have thyroid nodules, and 211 (57.0%) subjects had higher sugar metabolism, regardless of having thyroid nodules. No statistical correlations were observed among nodule size, nodule location,and higher sugar metabolism, however, noticeable relationships were observed between the shape of the cells on thyroid ultrasonography and FDG uptake of PET. In cases of papillary thyroid cancer, there was higher FDG uptake, compared to benign lesions in particular, SUVmax of the papillary thyroid cancer showed a significantly elevated level of FDG uptake.

Despite its limited usefulness in identifying the characteristics of thyroid nodules being benign or malignant, PET is appropriate for evaluation of the malignancy of thyroid cells