Computerized Study with 201T1 of the Cold Thyroid Node

The rational use of 201Tl scintigraphy in the evaluation of differentiated thyroid cancer

Fifteen patients with differentiated thyroid cancer were examined following 131I thyroid ablation, of these seven were examined after radio-iodine therapy to disseminated neck cancer. They had no further radio-iodine uptake and were evaluated using a 201Tl scan. In thirteen patients there was a good correlation between the results and the clinical diagnosis, showing no uptake in seven subjects with negative clinical findings, and positive delineation of tumour tissue in the neck region in six patients. The remaining two patients with lymph node metastases after previous radio-iodine irradiation showed marked clinical regression of the metastases with absent uptake of both 131I and 201Tl, probably due to radiation-induced changes. The comparison of thallium scans with plasma thyroglobulin levels showed certain differences (high plasma thyroglobulin without any proof of remaining thyroid tissue in one patient and normal/low plasma thyroglobulin in the presence of a tumour in two patients) but both measurements could give additional information. It is believed that while in the differential diagnosis of a thyroid nodule no important information could be expected of scanning (compared with the high value of aspiration biopsy), the evaluation of patients without 131I uptake by 201Tl scans could provide important information for further therapy.

Kinetics of 201Tl uptake in adenomas and well-differentiated carcinomas of the thyroid. A double isotope investigation with 99Tcm and 201Tl

A visually increased uptake of 201Tl chloride corresponding to a 'cold' (131I or 99Tcm ) thyroid nodule is mostly seen in well-differentiated carcinomas but also often in follicular adenomas. Since a visually increased uptake of 201Tl can be due to an increased initial uptake and/or a delayed elimination, an extended dynamic investigation was performed in patients with well-differentiated carcinomas or with follicular adenomas. Data were collected in a dynamic simultaneous double isotope ( 99Tcm + 201Tl) study up to 50 min after intravenous administration. Adenomas could be significantly separated from carcinomas by the elimination (p = 0.0001), but not by the initial uptake.