Has double-phase MIBI scintigraphy usefulness in the diagnosis of hyperparathyroidism?

The usefulness of double-phase parathyroid technetium-99m-MIBI scintigraphy for the detection of hyperplastic parathyroid tissue has been described. The aim of the present study was to establish the effectiveness of this new technique in the morphological and functional assessment of parathyroid glands in patients with different types of hyperparathyroidism. We performed 99mTc-MIBI scintigraphy (MIBI) and neck ultrasonography in 38 patients with primary (n=16) or secondary (n=22) hyperparathyroidism. All patients underwent surgical neck exploration, removing a total of 84 parathyroid glands. Before and after surgery, blood intact parathyroid hormone (iPTH) was measured peripherally and in both the right and left internal jugular veins. In patients with primary hyperparathyroidism, ultrasonography showed one enlarged gland in 11 cases (69%), while MIBI was positive in 15 (94%) (including two ectopic glands). The sensitivity of MIBI (93%) was greater than that of ultrasonography (68%), with a similar specificity (100 and 97%, respectively). In patients with secondary hyperparathyroidism, there was a discrepancy between both imaging modalities in 29 glands (33%). The sensitivity of both techniques was similar (41 and 54%, respectively), with the same specificity (89%). There were more difficulties in detecting the upper than the lower pathological glands. MIBI reflected more accurately the functionality of the glands, and ultrasonography has a better correlation with the volume and weight. In conclusion, Tc-99m-MIBI scintigraphy is a good technique to identify parathyroid hyperfunctioning tissue in cases of primary hyperparathyroidism and to detect ectopic glands, but it does not give significantly better results than conventional ultrasonography in patients with secondary hyperparathyroidism.