Early and Delayed Imaging of Tc-99m HMPAO Versus Tl-201 in Benign and Malignant Thyroid Tumors Similar Uptake but Different Retention

The authors performed both Tc-99m HMPAO and TI-201 scintigraphy in 30 patients with thyroid tumors (21 papillary adenocarcinoma, three solid follicular adenoma, six adenomatous goiter with cystic degeneration). Increased accumulation of both Tc-99m HMPAO and TI-201 was seen in 14 patients with papillary adenocarcinoma and three with solid follicular adenoma, whereas two patients with papillary adenocarcinoma had low accumulation of both tracers. Of the six patients with adenomatous goiter with cystic degeneration, four had low accumulation of both Tc-99m HMPAO and TI-201, and one patient had low accumulation of Tc-99m HMPAO only. Iso accumulation (same accumulation as the normal thyroid) of Tc-99m HMPAO was seen in five patients with papillary adenocarcinoma and one with adenomatous goiter. The distribution of Tc-99m HMPAO in the thyroid tumors and normal thyroid tissue was independent of time from 2 to 120 minutes after injection. The results of dynamic studies using Tc-99m HMPAO suggested that the accumulation of Tc-99m HMPAO in thyroid tumors reflected mainly tumor blood flow. The resultant Tc-99m HMPAO images were essentially similar to the TI-201 images obtained 10 minutes after injection. Tc-99m HMPAO imaging can be a suitable substitute for TI-201 imaging, and it may possibly be used to estimate tumor blood flow in patients with thyroid tumors