The usefulness of [131I]-metaiodobenzylguanidine ([131I]-MIBG) scintigraphy performed one week after administration in diagnosing pheochromocytoma.

BACKGROUND: Imaging performed 36-48 h after metaiodobenzylguanidine (MIBG) injection is being widely used in the diagnosis of pheochromocytoma. However, there are some difficult cases to diagnose due to a high concentration of MIBG remaining in the background. We studied the significance of scans on the 7th day after MIBG injection when the concentration of MIBG in the background has declined.

METHODS: Imaging was carried out on 11 cases before operation, five cases (eight times) after operation and 12 cases which had been strongly suspected of being pheochromocytoma, but later proved to be non-pheochromocytoma.

RESULTS: In all the cases of pheochromocytoma, except one, the tumor imaging was clear 24-72 h after MIBG injection. As for the images after operation and those of the 12 non-pheochromocytoma cases, the scintigram made on the 7th day proved the negative pheochromocytoma.

CONCLUSION: This approach was very effective not only for finding early small pheochromocytomas and the remnants of tumors after resection, but also in diagnosing non-pheochromocytoma.