Final answer:
Meta-iodobenzylguanidine (MIBG) serves as an analog to norepinephrine; it is used in both diagnostic imaging and the treatment of certain neuroendocrine tumors.
Step-by-step explanation:
Meta-iodobenzylguanidine (MIBG) acts as an analog to the natural neurotransmitter norepinephrine. It is similar in structure to norepinephrine and can be used to diagnose and treat certain types of cancer, specifically neuroendocrine tumors, such as pheochromocytoma. MIBG can be used diagnostically when labeled with radioactive iodine (123I) because it is taken up by adrenergic tissues, allowing for imaging of the tissues with a gamma camera. For therapeutic purposes, MIBG is labeled with a different isotope, usually 131I, to deliver a higher dose of radiation to cancerous cells expressing norepinephrine transporters.