Quantitative comparison of technetium-99m tetrofosmin and thallium-201 images of the thyroid and abnormal parathyroid glands

The aim of the study was to quantitatively compare the scintigraphic images of the thyroid and abnormal parathyroid glands obtained with technetium-99m tetrofosmin and thallium-201 in patients with hyperparathyroidism. Forty-six patients with hyperparathyroidism underwent 201Tl (74 MBq), 99mTc-pertechnetate (74 MBq) and 99mTc-tetrofosmin (555–740 MBq) scintigraphy in a single session. Image analysis included the computation of the thyroid/background ratio in the whole study population and the parathyroid/background ratio, parathyroid/thyroid ratio and diagnostic sensitivity in 17 patients who underwent parathyroid surgery. The pertechnetate subtraction technique was used. 201Tl and 99mTc-tetrofosmin showed a similar thyroid/background ratio (1.79±0.41 and 1.81±0.47, respectively, P=NS); however, 99mTc-tetrofosmin showed a higher parathyroid/background ratio than 201Tl (2.06±0.54 vs 1.79± 0.50, P=0.007). Despite the superior quality of 99mTc-tetrofosmin images, both tracers showed identical sensitivity in detecting enlarged parathyroid glands in patients with primary hyperparathyroidism (89%) and in those with secondary hyperparathyroidism (50%).