Magnetic resonance imaging (MRI) uses radio waves and a strong magnetic field rather than x-rays to provide remarkably clear and detailed pictures of internal organs and tissues. This technique has proved very helpful to radiologists in diagnosing tumors of the brain as well as disorders of the eyes and the inner ear. It requires specialized equipment and expertise and allows evaluation of some body structures that may not be as visible with other imaging methods.

MRI is the most sensitive exam for brain tumors, strokes and certain chronic disorders of the nervous system such as multiple sclerosis. In addition, it is a useful means of documenting brain abnormalities in patients with dementia and it is commonly used for patients with disease of the pituitary gland. MRI can detect tiny areas of tissue abnormality in patients with disease of the eyes or the inner ear.

Bone is better imaged by conventional x-rays, and CT is preferred for patients with severe bleeding, acute trauma or who because of their medical condition are unable to tolerate an MR scan procedure. MRI may not always distinguish between tumor tissue and edema fluid and does not detect calcium when this is present within a tumor. In most cases the exam is safe for patients with metal implants but there are a few exceptions, so patients should inform the technician of an implant prior to the test. The exam must be used cautiously in early pregnancy. MRI often costs more than CT scanning.