Quantitative aspects of thyroid scintigraphy with pertechnetate (99mTcO4-) in cats

Thyroidal 99mTcO4- (pertechnetate) uptake percentages were determined in unanesthetized euthyroid (n = 13) and hyperthyroid (n = 18) cats. Maximal uptakes were observed 60 minutes after IV injection of the radionuclide and ranged from 0.3 to 3.9% of the dose in euthyroid cats (median 2.23%) and from 5.2% to 23.9% of the dose in hyperthyroid cats (median 14.8%) (P < .05). There were no overlaps in pertechnetate uptake percentages during any of the intervals evaluated. It is concluded that the optimal time for visualization of the thyroid by 99mTcO4(-)-scanning is 60 minutes after IV injection of the radionuclide. Calculation of the percentage uptake is of additional diagnostic value.