1997 Volume 88 Issue 9 Pages 795-800
(Background) Recent studies have shown that 99mTc-methoxy-isobutyl-isonitrile (99mTc-MIBI), a new agent for myocardial perfusion imaging, can be successfully applied to parathyroid imaging. We evaluated the efficacy of 99mTc-MIBI scintigraphy for preoperative localization of enlarged parathyroid glands in patients with hyperparathyroidism.
(Patients and Methods) From June 1994 to September 1996, 24 patients with biochemical confirmation of hyperparathyroidism were studied with 99mTc-MIBI scintigraphy prior to operation. Eleven patients had primary hyperparathyroidism (PHPT) and 13 had secondary hyperparathyroidism (SHPT) associated with chronic renal failure, including one patient with recurrent disease after subtotal parathyroidectomy. A positive 99mTc-MIBI scan for an enlarged gland was difined as an area of persistent focal uptake on the delayed image acquired at 150min after intravenous injection of 600MBq of 99mTc-MIBI.
(Results) Of 11 patients with PHPT, 10, were found to have solitary parathyroid adenomas at surgery and one patient had primary hyperplasia. 99mTc-MIBI scintigraphy accurately detected 9 of 10 adenomas and 2 of 3 hyperplastic glands with no false positive results. Both of the two glands that were not detected by 99mTc-MIBI weighed 200mg. The mean weight of the 11 glands that were visualized was 1264mg (range 300-4300mg). The sensitivity and predictive value positive for PHPT were 84.6% and 100%, respectively. In 13 patients with SHPT, all of 49 parathroid glands were identified during surgery, with 43 hyperplastic glands and 6 normal-size glands. Of 43 hyperplastic glands, 28 were detected by 99mTc-MIBI and there was significant difference between the mean weight of these 28 glands (999mg, range 290-2630mg) and that of the 15 nonimaged hyperplastic glands (283mg, range 90-540mg). None of the six normal glands were imaged with 99mTc-MIBI. One patient had a false positive scan caused by a thyroid nodule. The sensitivity and predictive value positive for SHPT were 65.1% and 96.6%, respectively.
(Conclusion) 99mTc-MIBI scintigraphy is an excellent imaging method for localization of enlarged parathyroid glands in patients with hyperparathyroidism, especially with PHPT. However, it has the difficulty to demonstrate enlarged glands smaller than 300mg in weight.
