Comparison of Iodobenzylguanidine Imaging with Computed Tomography in Locating Pheochromocytoma*

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Abstract
Ninety-nine patients suspected of having pheochromocytoma were studied with [131I]metaiodobenzylguanidine scintigraphy, and 92 of them were studied with computed tomography (CT). In 49 patients, the diagnosis was ruled out; in 3 patients, it remained doubtful; and in 47 patients, it was confirmed. Two patients had tumors that did not secrete epinephrine or norepinephrine, and 45 had secreting pheochromocytomas. In these latter patients, there were 4 false negative [131I]metaiodobenzylguanidine scans, all intraadrenal tumors, and 4 false negative CT scans, 3 extraadrenal and 1 intraadrenal tumors. For about 80% of the patients and/or the tumor sites, both methods were thus in agreement. They were complementary in the remaining 20%. The advantage of scintigraphy is to screen the whole body with high specificity and to locate extraadrenal sites or metastases of pheochromocytoma with better accuracy than CT. The limits of scintigraphy are the possibility of false negative scans in around 10% of patients, whereas CT visualizes more than 95% of intraadrenal tumors.