Double-phase Technetium 99m Sestamibi Scintigraphy for the Localization of Parathyroid Adenoma

Objective: The purpose of the present study was to evaluate the accuracy of double phase Tc sestamibi scintigraphy in the assessment of parathyroid glands in patients with hyperparathyroidism and to compare this method with the high-resolution ultrasonography. Methods: From August-1998 through August-2000, we performed Tc -MIBI scintigraphy (MIBI) and neck ultrasonography in 35 patients who were clinically and biochemically suspected of having hyperparathyroidism. All patients underwent surgical neck exploration. Before surgery, blood intact parathyroid hormone and serum calcium level were measured peripherally. Early and delayed cervical images of MIBI scans and neck ultrasonography were interpreted by two radiologists. The findings were compared to ultrasonography and scintigraphic results. The sensitivity and positive predictive values of both modalities for localizing the diseased glands were determined by comparing scan findings with pathological findings, which were considered the gold standard. Results: All resected glands were abnormal. They belonged to 25 patients with a single adenoma, two patients with ectopic glands, two patients with double adenomas and 6 patients with hyperplastic parathyroid glands. The sensitivity and positive predictive values for localizing the diseased glands in patients with hyperparathyroidism were 91% and 97%, respectively for Tc 99m MIBI. The values were 74% and 100%, respectively, for ultrasonography. Tc 99m MIBI sensitivity was higher in patients with parathyroid adenomas (96%) than that in patients with parathyroid hyperplasia (67%). Conclusion: Our results demonstrate that Tc sestamibi scintigraphy is highly accurate in identifying parathyroid adenoma when performed by an experienced radiologist. It is helpful in preoperative localization of parathyroid adenoma in patients with suspected ectopic glands. Nevertheless, because of the greater accessibility, lower costs and simplicity, ultrasonography could be used as a screening modality for parathyroid adenoma localization.