Chest uptake after thyroid remnant ablation
History
46-year-old woman. Total thyroidectomy and central neck dissection for a 4.5 cm papillary carcinoma (follicular variant) with extensive vascular invasion, pT3a N1a. Stimulated thyroglobulin 180 ng/mL before treatment (antibodies negative); preoperative chest CT reported as clear. Given 3.7 GBq ¹³¹I after recombinant TSH; post-therapy scan on day 7.
Step 1 · Post-therapy scan
Apart from the thyroid bed and the expected salivary, gastric, bowel and bladder activity, there is diffuse activity throughout both lungs, sparing the heart and stopping at the diaphragm. What does the chest activity represent?