Optimal pinhole techniques for preoperative localization with Tc-99m MIBI for primary hyperparathyroidism

Purpose: Technetium-99m-labeled 2-methoxyisobutylisonitrile (Tc-99m MIBI) h as been used extensively to localize parathyroid adenomas before operation. Imaging techniques vary widely, and the aim of this study was to determine the optimal time of delayed imaging and the value of routine correlative p ertechnetate thyroid imaging. Materials and Methods: In this study, preoperative parathyroid localization was performed using pinhole anterior and oblique images (15 minutes and 2 and 4 hours after injection) with correlative pertechnetate thyroid images. Ninety-seven patients underwent dual- or triple-phase Tc-99m MIBI imaging and correlative pertechnetate thyroid imaging before surgery. Two nuclear m edicine physicians blinded to the surgical findings interpreted all availab le images and various Tc-99m MIBI image combinations at 15 minutes alone; 1 5 minutes and 2 hours, 15 minutes and 4 hours; and 15 minutes and 2 and 4 h ours each with and without correlative pertechnetate thyroid imaging. Results: Ninety parathyroid adenomas were detected in 86 patients. The opti mal results were achieved with 15-minute and 2- and 4-hour Tc-99m-MIBI imag es, with correlative thyroid scans resulting in a sensitivity rate of 88%. Fifteen-minute and 2-hour Tc-99m-MIBI images and correlative thyroid scans and 15-minute and 4-hour Tc-99m MIBI images and correlative thyroid scans p roduced similar results (sensitivity rate, 86% and 83%, respectively; P = n ot significant). Compared with all Tc-99m MIBI image combinations alone, th e addition of the routine correlative thyroid scan significantly improved s ensitivity and also improved reporter confidence in 45% of studies. Conclusions: Of the pinhole techniques compared, 15-minute and 2-hour Tc-99 m MIBI images with correlative thyroid scanning may be the preferred imagin g protocol, because this yields results similar to imaging for as long as 4 hours after injection in a shorter, more logistically acceptable imaging t ime.