What it is. The MRI scan uses radio waves, magnetic fields, and computer analysis to create a picture of body tissues and structures.

Who should not have one. Be sure you let your doctor know if you have a metal heart valve, pacemaker, or metal fragment in your eye or head. If you do, you shouldn't have an MRI.

Who needs one. Your doctor may recommend an MRI or CT scan if you have any of these symptoms:

  • decreased alertness
  • onset of pain with exertion, sexual intercourse, coughing, or sneezing
  • worsening of condition
  • rigidity in the back of the neck
  • loss of consciousness, sudden weakness, or paralysis
  • numbness

Your doctor may also recommend an MRI or CT scan for any of the following reasons.

  • You are older than age 50 years and are having your first headaches.
  • You are having the worst headache you've ever had.
  • Your headache does not fit any defined pattern.

How it's done. During a CT scan, a doctor may inject a contrast dye with iodine into your body. A special type of photograph is then taken of a specific site. The CT scan can be more definitive in picking up problems in your head or brain. These tests are used to locate skull fractures, cancers, sinus problems, concussions, hematomas, and other medical problems. There is no pain or discomfort, but you must lie very still during the test.