The thallium-201 time activity curve in thyroid cancer: a role for the detection of metastases.

The Tl-201 Cl time activity curves were evaluated in 17 patients with histologically proven benign nodules and papillary carcinoma of the thyroid gland. In the dynamic studies, the uptake at the region of interest was counted every 10 sec for 20 min after the intravenous injection of 2mCi Tl-201 Cl. The curves from frame 21 to 100 were transformed to linear plots for clinical evaluation. Papillary carcinoma could not be differentiated from benign lesions by means of the values of the washout rate. However, the "relative washout rate" in papillary carcinoma was lower than that of benign lesions (P less than 0.05). Although the average values of the "relative extrapolated uptake" in papillary carcinoma appeared to be greater than those in benign lesions, the difference was not statistically significant. The difference in the washout rates between lymph node metastases and local recurrences, and pulmonary metastases of the papillary carcinoma was significant (P less than 0.05).