Magnetic resonance imaging is abbreviated MRI. An MRI might be one test a doctor will use to diagnose a pancreatic endocrine islet cell tumor. Before an MRI is done, a dye is injected into a vein of the person undergoing the test. This dye is attracted to any tumor cells in the body and accumulates near them. The person then lies on a flat surface that is guided into a tube-shaped object. This object uses a combination of magnets and radio waves connected to a computer to produce a picture of the body. Any buildup of dye noted in one area of the body can indicate a tumor.