Brain & Nervous System Health Center

How It Is Done continued...

During the test you will lie on your back on a table that is part of the MRI scanner. Your head, chest, and arms may be held with straps to help you lie still. The table will slide into the space with the magnet. A device called a coil may be placed over or wrapped around your head. Some MRI machines (called open MRI) are now made so that the magnet is not around your whole body. See pictures of a standard MRI machine and an open MRI machine .

Some people feel nervous (claustrophobic) inside the MRI magnet. If this keeps you from lying still, you can be given a medicine (sedative) to help you relax. Open MRI machines may be helpful if you are claustrophobic.

Inside the scanner you will hear a fan and feel air moving. You may also hear tapping or snapping noises as the MRI pictures are taken. This is normal. You may be given earplugs or headphones with music to reduce the noise. It is very important to hold completely still while the scan is being done. You may be asked to hold your breath for short periods of time.

During the test, you may be alone in the scanner room. The technologist will watch you through a window. You will be able to talk through a speaker.

If contrast material is needed, the technologist will put it in an intravenous (IV) line in a vein in your arm or hand. The material may be given over 1 to 2 minutes. Then more MRI scans are done.

An MRI test usually takes 30 to 60 minutes but can take as long as 2 hours.

How It Feels

You will not have pain from the magnetic field or radio waves used for the MRI test. The table you lie on may feel hard and the room may be cool. You may be tired or sore from lying in one position for a long time.

If a contrast material is used, you may feel some coolness and flushing as it is put into your IV.

In rare cases, you may feel:

• A tingling feeling in the mouth if you have metal dental fillings.
• Warmth in your head. This is normal. Tell the technologist if you have nausea, vomiting, headache, dizziness, pain, burning, or breathing problems.

Risks

There are no known harmful effects from the strong magnetic field used for MRI. But the magnet is very powerful. The magnet may affect pacemakers, implantable cardioverter-defibrillators (ICDs), artificial limbs, and other medical devices that contain iron. The magnet will stop a watch that is close to the magnet.

Metal pieces in the eyes can damage the retina. If you might have metal pieces in your eye, an X-ray of the eyes may be done before the MRI. If metal is found, the MRI will not be done.