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 asthallium-technetium subtraction imaging in the preoperative localization ofhyperplastic parathyroid glands in patients with renal failure. Reportshave suggested that 50% of glands can be identified correctly by thismethod. The aim of this study was to improve on previous results anddemonstrate that Tc-99m MIBI imaging has an important place in thepreoperative work-up of these patients. Methods.Eighteen patients on renal replacement therapy were studied. All hadtertiary hyperparathyroidism and had Tc-99m MIBI imaging prior toparathyroidectomy. A refined reporting method was employed. The imagingresults were compared to the subsequent surgical and histological findings.Results. In the 12 patients in whom serum parathyroidhormone levels fell postoperatively to within or below the normal range, 38of 46 glands (82.6%) were correctly identified and located in the correctquadrant of the thyroid gland. There were two false positive results wherethe imaging predicted glands not subsequently found by the surgeon. In thepatients who had post-operative hyperparathyroidism, repeat Tc-99m MIBIimaging was able to locate accurately the site of the residual parathyroidtissue. Conclusion. Tc-99m MIBI imaging is able toidentify more than 80% of hyperplastic parathyroid glands in renal failurepatients if this reporting process is used, and locate them in the correctquadrant of the thyroid gland. Tc-99m MIBI imaging is of particular valuewhen re-exploration of the neck is required for post-parathyroidectomyhyperparathyroidism. These results represent a significant improvement onthe sensitivity of this imaging technique when compared to previouspublished data.