Localization of Pheochromocytoma: I-MIBG Scintigraphy Correlated with Computed Tomography

Received 11/13/2000; revised 2/1/2001; accepted 2/5/2001. For correspondence or reprints contact: Chiang-Hsuan Lee, M.D., Department of Nuclear Medicine, Chang Gung Memorial Hospital, 123, Ta-Pei Road, Niao Sung Hsiang, Kaohsiung Hsien, Taiwan, Tel: (886)7-7317123 ext. 2627, Fax: (886)77317123 ext. 2631, E-mail: [email protected] Background: This study aimed to evaluate the efficacy of iodine-131 meta-iodobenzylguanidin (I-MIBG) scintigraphy and computed tomography (CT) in localization of pheochromocytomas. Methods: We retrospectively evaluated 25 patients with pheochromocytomas in our hospital during 1987-1999. All of these patients received I-MIBG scintigraphy and CT examinations within one week. The pathologic confirmations were obtained in all of the patients. Results: Pheochromocytomas were localized in unilateral adrenal gland in 22 patients (88%) and in extraadrenal in 3 patients (12%). Overall sensitivity of the studies was 96% (24/25) for CT and 80% (20/25) for MIBG. CT failed to detect one perivesical lesion, and falsely detected two other lesions as pheochromocytomas (specificity 92%). MIBG scintigraphy failed to detect five lesions; three of these lesions were imaged while the patients were on labetalol therapy and the other two lesions were smaller than 3 3 3 cm in size. There were no false positive results by MIBG scintigraphy (specificity 100%). Combined use of these two imaging procedures correctly detected all of these pheochromocytomas. Conclusions: MIBG scintigraphy and CT are complementary in the localization of pheochromocytoma. CT has greater sensitivity than MIBG scintigraphy in abdomen sites. However, MIBG scintigraphy can provide specific functional confirmation of the CT findings and has the ability to screen the entire body, which is especially useful in the detection of extra-abdominal disease.