Sestamibi scan for preoperative localization in primary hyperparathyroidism

Various invasive and noninvasive localizing tests are available for the evaluation of primary hyperparathyroidism. The surgical success in primary intervention exceeds 90% without localization studies. However, localization tests are absolutely essential for re-exploration and in certain select circumstances, even in primary exploration. The traditional noninvasive localization studies include the sonogram, thallium-technetium scan, computed tomography (CT) scan, and magnetic resonance imaging (MRI). The purpose of this report is to review our recent experience with sestamibi scan. The sestamibi scan appears to be the most sensitive and accurate noninvasive test available today.

Technetium 99m sestamibi has recently been used for parathyroid localization, in conjunction with iodine123 subtraction. We have evaluated 24 patients with suspected primary hyperparathyroidism to study the role of technetium 99m sestamibi scan. Tc-sestamibi was used either with or without iodine123 for subtraction of thyroid activity.

None of these patients had renal failure or secondary hyperparathyroidism. Of 24 patients, the parathyroid adenoma was localized by scintigraphy in 19 patients. Twenty patients underwent surgical exploration. In 17 patients there was a complete correlation between the imaging study and the operative findings (positive predictive value, 89%). There were no false positives in this series. The interpretation of the parathyroid images was relatively easy; however, the depth of the adenoma could not be predicted, based on the scan alone. The largest adenoma weighed 2.7 g, the smallest, 700 mg.

This newer radiopharmaceutical, technetium 99m sestamibi, appears to be quite useful and accurate in the preoperative localization of patients with primary hyperparathyroidism. Parathyroid enlargement can also be studied by sestamibi imaging alone if delayed imaging is performed.