Parathyroid imaging with technetium-99m-sestamibi: an initial institutional experience

The ideal method for preoperative localization of abnormal parathyroid glands has yet to be determined. Technetium-99m-sestamibi, previously used for myocardial perfusion studies, has recently been introduced for parathyroid imaging.

From August 1991 to September 1993, 44 patients underwent Tc-99m-sestamibi scanning (45 scans) and surgical exploration for hyperparathyroidism at our institution. These 44 patients form the database for this retrospective study. Twenty-eight patients had persistent hyperparathyroidism, six had recurrent disease, three had prior thyroid operation, and seven underwent first time neck operations. The nature of disease was complex and varied: single gland, 26; primary hyperplasia, 5; multiple endocrine neoplasia type 1, 5; familial, 3; secondary or tertiary, 5. One patient with single gland disease and one patient with multiple endocrine neoplasia type 1 had parathyroid carcinoma. All patients had biochemical confirmation of hyperparathyroidism.

Twenty-six (58%) of 45 scans accurately predicted the location(s) of all abnormal gland(s) involved (true positive). Surgical removal of these glands was curative. Sixteen (36%) of 45 scans were false negative because they did not show all abnormal glands involved; however, 7 of these 16 scans did localize at least one abnormal gland. The overall sensitivity of this test was 62% when all abnormal glands were considered but increased to 79% with the demonstration of at least one abnormal gland. These values increased to 80% and 90% (p = 0.03), respectively, in the last 20 patients when the injected dose of Tc-99m-sestamibi was increased from 10 to 15 mCi. Thirty-seven of 44 patients were cured after operation. Six of the seven patients who experienced surgical failure had multigland disease, one of which was malignant. Sestamibi scans correctly identified abnormal cervical glands in 18 (58%) of 31 patients and abnormal mediastinal glands in six (75%) of eight patients.

Tc-99m-sestamibi scanning is helpful in the reoperative setting as an adjunct to localizing abnormal parathyroid tissue. A higher percentage of positive tests occurs in patients with mediastinal and single gland disease. A higher dose of Tc-99m-sestamibi (15 mCi) significantly improves test sensitivity.