A procedure used to find neuroendocrine tumors, such as neuroblastomas and pheochromocytomas. A small amount of a substance called radioactive iobenguane is injected into a vein and travels through the bloodstream. Neuroendocrine tumor cells take up the radioactive iobenguane and are detected by a scanner. Also called metaiodobenzylguanidine scan and MIBG scan.