IN-VIVO UPTAKE OF TECHNETIUM-99M-SESTAMIBI BY PARATHYROID-GLANDS IN COMPARISON TO SURROUNDING TISSUES OF THE NECK

Technetium-99M-sestamibi (Tc-99M-sestamibi) has recently been proven t o be a sensitive and specific agent for imaging of parathyroid disease ; however, the selective nature of its uptake by different tissues has not been investigated. Fifteen consecutive patients undergoing neck e xploration for hyperparathyroidism were given 3 to 15 mCi of Tc99M-ses tamibi at various times before surgery, and at the time of exploration , samples of parathyroid tissue, blood, fat, muscle, and thyroid were taken from the neck. All samples were carefully weighed and counts of radioactivity were measured. Activity was normalized to counts per gra m of tissue and counts of radioactivity were compared using a multiple range analysis of variance test. Mean counts per gram (+/- SE) in abn ormal parathyroid tissue (adenomas and hyperplastic glands; 1.1 x 10(6 ) +/- 2.7 x 10(6) were significantly higher than in any of the other t issues measured (P < 0.05): thyroid, 7.0 x 10(4) +/- 1.6 x 10(4); musc le, 8.9 x 10(4) +/- 2.1 x 10(4); fat, 2.1 x 10(4) +/- 4.2 x 10(3); and blood, 9.8 x 10(3) +/- 2.3 x 10(3). Mean ratios of counts (+/- SE) of abnormal parathyroid tissue to other tissues were found to be as foll ows: thyroid, 35.3 +/- 12.6; muscle, 17.4 +/- 6.2; fat, 80.7 +/- 20.0; and blood, 161.0 +/- 31.6. From these data, Tc-99M-sestamibi clearly exhibits significantly higher uptake in abnormal parathyroid tissue re lative to other tissues measured in the neck. This increased uptake in parathyroid gland tissue accounts for the utility of Tc-99M-sestamibi in localization studies for hyperparathyroidism. Quantification of in vivo uptake of Tc-99M-sestamibi may help refine techniques for improv ed localization of hyperfunctional parathyroid glands.