Technetium-99m tetrofosmin imaging in patients with subacute thyroiditis.

We studied the significance of technetium-99m tetrofosmin scintigraphy in patients with subacute thyroiditis (SAT). Six patients with SAT, who had painful goitre with thyrotoxicosis, underwent 99mTc-pertechnetate scintigraphy and 99mTc-tetrofosmin imaging during the acute and recovery stages of SAT. The thyroid uptake ratio of tetrofosmin was compared with the clinical parameters associated with SAT. 99mTc-pertechnetate scintigraphy showed markedly reduced uptake in the thyroid during the acute stage of SAT, suggesting that the appropriate metabolic pathway is not functioning. Conversely, 99mTc-tetrofosmin images showed diffuse increased uptake in the thyroid region on early and delayed imaging. Tetrofosmin images in the acute stage and in the recovery stage of SAT showed different clearance curves for tetrofosmin uptake. The uptake ratio assessed as thyroid uptake/background (T/B) correlated with the serum C-reactive protein concentration. In conclusion, 99mTc-tetrofosmin uptake may reflect the inflammatory process associated with SAT, and thus this tracer may have potential as a marker of disease activity and severity.