What the risks are:

MRI uses no radiation. To date, no side effects from the magnetic fields and radio waves have been reported.

The most common type of contrast (dye) used is gadolinium. It is very safe. Allergic reactions to the substance rarely occur. However, gadolinium can be harmful to patients with kidney problems who require dialysis. If you have kidney problems, please tell your health care provider before the test.

The strong magnetic fields created during an MRI can cause heart pacemakers and other implants to not work as well. It can also cause a piece of metal inside your body to move or shift.

Special considerations:

Tests that may be done instead of an MRI of the head include:

• Cranial CT scan
• Positron emission tomography (PET) scan of the brain
• Skull x-ray

A CT scan may be preferred in the following cases, since it is faster and usually available right in the emergency room:

• Acute trauma of the head and face
• Bleeding in the brain (within the first 24 to 48 hours)
• Early symptoms of stroke
• Skull bone disorders and disorders involving the bones of the ear