False-Positive 131I Uptake in Fixed Prosthetic Denture

Iodine-131 whole-body scan is used to detect functional metastases in patients with history of differentiated thyroid carcinoma. Nonphysiological uptakes are usually interpreted as thyroid metastases. However, false-positive uptakes, such as nonthyroidal tumors and contamination from body secretions, have been reported. We report a case of incidental finding of tracer activity in a patientʼs prosthetic denture, which was localized by SPECT/CT. There is no evidence of dental or periodontal disease clinically or radiologically, and the serum thyroglobulin was at undetectable level. Potential false-positive activity related to dental conditions should be recognized and not be mistaken as metastatic disease.