The diagnostic utility of dual phase Tc-99m sestamibi parathyroid imaging

Primary hyperparathyroidism is a disease of uncertain etiology that results from hypersecretion of parathyroid hormone (PTH) by the parathyroid gland. In most institutions, the preferred imaging protocol utilizes a dual-phase technique with Tc-99m sestamibi which is reported to be more sensitive than earlier protocols involving TI-201 with Tc-99m pertechnetate subtraction. The purpose of this study is to evaluate the accuracy and clinical utility of Tc-99m sestamibi dual-phase scintigraphy for localizing hyperfunctioning parathyroid tissue.

We retrospectively reviewed thirty-nine consecutive hyperparathyroid patients who received a dual-phase Tc-99m sestamibi parathyroid scan. Thirty-seven of the subjects subsequently underwent a bilateral neck exploration and parathyroidectomy. Each scan interpretation was then correlated with the histopathologic diagnosis and the patients' post-surgical clinical course.

The sestamibi dual-phase imaging protocol correctly localized 21 of 25 parathyroid adenomas and identified 8 out of 10 cases of hyperplasia. Our overall sensitivity and specificity were 83% and 75%, respectively. In addition, four of the adenomas were successfully localized intraoperatively using a gamma probe.

Parathyroid imaging with sestamibi appears to be superior to TI-201/Tc-99m pertechnetate subtraction based on the reported results of both techniques at various institutions. Dual-phase sestamibi imaging appears to be useful and cost-effective for presurgical localization of hyperfunctioning parathyroid tissue. In addition, sestamibi imaging in conjunction with an intraoperative probe is a very promising technique that has the potential to provide both localization information of a suspected parathyroid adenoma and to facilitate its surgical removal by reducing operation time.