Parathyroid imaging: comparison of 201Tl-99mTc subtraction scintigraphy, computed tomography and ultrasonography

From 1982 to 1985, twenty-nine patients with suspected hyperparathyroidism were examined using 201Tl-99mTc subtraction scintigraphy (Tl-Tc), computed tomography (CT) and ultrasonography (US). For diagnosing neoplasm (adenoma or cancer), the sensitivities of the three procedures were 80 per cent or more, with no statistically significant differences. For diagnosing hyperplasia of the parathyroid glands, CT scan had the highest sensitivity (47 per cent). The most frequent source of error was minimally enlarged glands, weighing less than 500 mg. The second highest source of error was thyroid nodules, such as adenomatous goiter or cancer. Serum calcium and c-PTH levels were significantly higher in those with a parathyroid neoplasm than in those with hyperplasia (p less than 0.01, p less than 0.05, respectively). We concluded that hyperplasia is less easy to detect than neoplasm, and CT scan is superior to Tl-Tc or US scan for localizing hyperplasia.