Clinical Evaluation of Thyroid Imaging with 201Tl-Chloride

Clinical value and limitation of thyroid imaging with 201T1C1 were studied. The positive rate of 201T1 was 82% in 22 malignant thyroid lesions and 46% in 37 benign lesions. A 201T1 positive image was obtained when a lesion was parenchymatous and a 201T1 negative one when it was cystic, filled with colloid or hyaline and had massive necrosis or bleeding. Thus 201T1 Cl localized in a parenchymatous lesion and did not in a nonparenchymatous one regardless of a malignant or benign disease. An increasing positive lesion in contrast with the surrounding thyroid tissue implies that it may be malignant and a decreasing one benign as a results of review of serial scintiphotos. Scintigraphic methods with 131I and 201T1 are complementary each other and a 201T1 negative image itself has a high diagnostic value but it seems to be better to attach much value to the finding of imaging with 131I when a 201T1 positive image is obtained.