201Tl for the differential diagnosis of cold thyroid nodules.

We used 201Tl-chloride for studying and differentiating thyroid areas shown to be 'cold' in previous 131I or 99mTc scanning. We investigated sixteen thyroid neoplasms that were removed surgically shortly afterwards. We found an intense intranodular accumulation of 301T1 in five scintigraphs shown to be of histologically malignant neoplasms, and an intense accumulation also in one of those shown to be histologically benign. We did not detect any 201Tl-chloride accumulation in two cases of thyroiditis; one of these had shown an intense accumulation in a previous 131Cs scintigram.