Preoperative Localization in Primary Hyperparathyroidism: Comparison of Tc99m MIBI Scan and Tl201/Tc99m Subtraction Scan

Kang, Kyung Ho; Chang, Myung Chul; Noh, Dong Young; Youn, Yeo Kyu; Moon, Byung In; Oh, Seung Keun

Abstract

PURPOSE: Recently Tc99m MIBI (methoxyisobutylisonitrile) has been described as an alternative to thallium for localizing parathyroid lesions. The purpose of this study was to compare the efficacy of a Tc99m MIBI scan with a Tl201/Tc99m subtraction scan for localizing parathyroid lesions in patients with primary hyperparathyroidism.
METHODS
Among 31 cases of primary hyperparathyroidism operated on at the Department of Surgery, Seoul National University Hospital from January 1997 to June 2001, a Tl201/Tc99m subtraction scan was performed on 16 patients and a Tc99m MIBI scan on 22 patients. Seven patients underwent both.
RESULTS
The pathology was a single adenoma in 28 patients, a hyperplasia in 1 patient and a carcinoma in 2 patients. Hypercalcemia was controlled postoperatively in all cases. The sensitivities of the Tl201/Tc99m subtraction scan and Tc99m MIBI scan were 53.3% and 86.4%, respectively. The positive predictive values were 100% of the two study groups.
CONCLUSION
We concluded that the better accuracy, superior image quality and lower cost of Tc99m MIBI scan will make it the new radiopharmaceutical parathyroid scan of choice. A unilateral approach can be used with a high degree of success, as in case of a preoperatively localized single parathyroid adenoma, which was confirmed when surgical exploration identified of a normal ipsilateral gland.