I131/I123 Metaiodobenzylguanidine (mIBG) Scintigraphy help locate and diagnose certain types of tumors in the body. MIBG is a substance that gathers in some tumors, particularly neuroblastoma tumors. When MIBG is combined with radioactive iodine (tracer), it provides a way to identify primary and metastatic (spread) disease. MIBG scans are helpful for locating both bone and soft tissue tumors.