Technetium-99m tetrofosmin parathyroid imaging in patients with primary hyperparathyroidism

OBJECTIVE: To confirm the clinical significance of 99mTc-tetrofosmin imaging for the localization of hyperfunctioning parathyroid glands in patients with primary hyperparathyroidism. METHODS: All patients were imaged with 99mTc-tetrofosmin at 10 minutes and 2 hours after radiotracer injection, and with ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI). The parathyroid/thyroid uptake ratio of 99mTc-tetrofosmin (P/T uptake ratio) was calculated. PATIENTS: Twenty patients with primary hyperparathyroidism were referred to our clinic, underwent surgical neck exploration or mediastinotomy and were diagnosed as having parathyroid adenoma. These patients were investigated for the preoperative localization by 99mTc-tetrofosmin scintigraphy. RESULTS: 99mTc-tetrofosmin imaging demonstrated focal uptake in 19 out of 20 patients with parathyroid adenoma. Two of the lesions were ectopic. US identified 17 parathyroid glands. CT and MRI initially detected 17 parathyroid glands. However, two additional parathyroid glands were localized on repeated CT and MRI in tandem with the results of the 99mTc-tetrofosmin imaging. Thus, the sensitivity and specificity of tetrofosmin imaging were 95% (19/20) and 95% (19/20); US, 85% (17/20) and 94% (16/17); initial CT, 85% (17/20) and 94% (16/17); and initial MRI, 88% (17/20) and 94% (16/17), respectively. The P/T uptake ratio at 2 hours after tetrofosmin injection was correlated with the serum concentration of intact PTH (rs=0.47, p<0.05) and the resected tumor weight (rs=0.53, p<0.05). CONCLUSION: 99mTc-tetrofosmin scintigraphy is useful for localization of parathyroid adenoma. Tetrofosmin uptake depends on the tumor weight and serum intact PTH levels.