Portrayal of pheochromocytoma and normal human adrenal medulla by m-[123I]iodobenzylguanidine: concise communication.

The radiopharmaceutical m-[131I]iodobenzylguanidine (I-131 MIBG), which is readily taken up by adrenergic vesicles, produces scintigraphic images of pheochromocytomas in man but rarely visualizes normal adrenal glands. Iodine-123 has many potential advantages over I-131 as a radiolabel for MIBG, including shorter half-life, freedom from beta emissions, and increased gamma-camera efficiency. In this study, diagnostic doses of MIBG labeled with I-131 and I-123, with nearly equivalent radiation dosimetry, were compared as imaging agents in eight patients with known or suspected pheochromocytoma. Images of superior quality were obtained with I-123 MIBG, and lesions not visualized using I-131 MIBG were portrayed. In addition, the normal adrenal medullae were visualized on the I-123 MIBG scintigrams in six out of eight patients.