Clinical research on physiological thymic uptake of ¹³¹I in post-operative patients with differentiated thyroid cancer

Objective: To explore the clinical features and ¹³¹I whole body scans (WBS)characteristics of physiological thymic uptake of ¹³¹I in post-operative patients with differentiated thyroid cancer (DTC). Methods: One thousand eight hundred and eighty-two WBS were performed on the 3-5 day after ¹³¹I therapy in post-operative patients with DTC between 2007 and 2013. On the basis of thyroglobulin and thyroglobulin antibody measurement, other imaging and clinical follow-up, the mediastinal activity was attributed to physiological thymic uptake of ¹³¹I. For such patients, their data were reviewed retrospectively. Results: Physiological thymic uptake of ¹³¹I were confirmed in 16 patients. All of them were under the age of 45. Fifteen patients received at least two therapeutic doses of ¹³¹I, and there was only one patient to be found physiological thymic uptake of ¹³¹I on the first treatment. The pattem of physiological thymic uptake of ¹³¹I was classified as 'diffuse' or 'dumbbell'. Thymic uptake of ¹³¹I became more prominent with repeated treatments. Conclusions: For the next appropriate treatment, it is essential to acknowledge that physiological thymic uptake of ¹³¹I in patients with DTC under the age of 45 is an important cause of false-positive WBS. (authors)