Technetium-99m methoxy isobutyl isonitrile (MIBI) imaging of the parathyroid glands in patients with renal failure

Background. Technetium-99m methoxy isobutyl isonitrile (Tc-99m MIBI) scintigraphy has been reported to be at least as reliable as thallium-technetium subtraction imaging in the preoperative localization of hyperplastic parathyroid glands in patients with renal failure. Reports have suggested that 50% of glands can be identified correctly by this method. The aim of this study was to improve on previous results and demonstrate that Tc-99m MIBI imaging has an important place in the preoperative work-up of these patients. Methods. Eighteen patients on renal replacement therapy were studied. All had tertiary hyperparathyroidism and had Tc-99m MIBI imaging prior to parathyroidectomy. A refined reporting method was employed. The imaging results were compared to the subsequent surgical and histological findings. Results. In the 12 patients in whom serum parathyroid hormone levels fell postoperatively to within or below the normal range, 38 of 46 glands (82.6%) were correctly identified and located in the correct quadrant of the thyroid gland. There were two false positive results where the imaging predicted glands not subsequently found by the surgeon. In the patients who had postoperative hyperparathyroidism, repeat Tc-99m MIBI imaging was able to locate accurately the site of the residual parathyroid tissue. Conclusions. Tc-99m MIBI imaging is able to identify more than 80% of hyperplastic parathyroid glands in renal failure patients if this reporting process is used, and locate them in the correct quadrant of the thyroid gland. Tc-99m MIBI imaging is of particular value when re-exploration of the neck is required for post-parathyroidectomy hyperparathyroidism. These results represent a significant improvement on the sensitivity of this imaging technique when compared to previous published data.