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  Magnetic Resonance Imaging (MRI)

What is an MRI?

Magnetic Resonance Imaging (MRI) is a diagnostic procedure that utilizes a large, strong magnet in order to produce a picture (image) of the internal structures of the human body such as the brain and spinal cord.  Magnetic Resonance Angiography (MRA) uses the same technology in order to produce an image of the arteries whereas Magnetic Resonance Venography (MRV) produces images of the veins.  The MRI machine is housed in a special room that provides protection for its powerful magnet.

Are there any risks?

The MRI is a safe and painless procedure.  There are no documented risks.  The safety of this procedure during pregnancy is unknown although there is no documented evidence of any risk.  It is still preferable, if at all possible, not to perform an MRI during the first trimester. 

How long the test will take?

It all depends on what specific test your doctor has requested: 
  • An MRI of the brain requires about 20 – 40 minutes. 
  • An MRI of the cervical spine requires about 20 – 30 minutes.
  • An MRI of the thoracic spine requires about 20 – 30 minutes.
  • An MRI of the lumbo-sacral spine requires about 20 – 30 minutes.
  • An MRI of the brachial plexus or lumbo-sacral plexus requires about 30 minutes.

The length of the study also depends on whether contrast material will be injected or not, and whether additional investigations such as MRA or MRV are requested.  MRI contrast agents assist the radiologist in better interpreting your MRI scan.

  • An MRA requires about 15 – 30 minutes
  • An MRV requires about 10 minutes
How to prepare for an MRI?

Because the MRI machine uses a large magnet, metallic objects and mechanical devices are not allowed into the examination room.  Metallic objects will fly across the room and mechanical devices will malfunction in the MRI room.  It is therefore requested that you not wear any jewelry or watches to the examination since they will have to be removed.   Comfortable clothing with as little as possible metal accessories is advised.  Mascara is to be avoided since it may contain a metallic base.  Hair pins or clips must be removed prior to the examination.  It is best to remove dental devices prior to the procedure.

You will be asked several questions prior to the MRI procedure in order to assure that there is no contraindication to performing the test.  The following special considerations apply:

You will be asked if you have ever undergone a surgical procedure.  Metallic clips, screws, stents, artificial valves or implants may prohibit you from having the MRI procedure.  Most, though not all, devices are now MRI compatible.

If you have a pacemaker, an implanted pump or a stimulation device such as a Deep Brain Stimulator (DBS) or Spinal Cord Stimulator you will not be able to undergo this procedure.

If you have any metallic fragments in your eyes you will not be able to undergo this procedure.  If you have fragments of explosive devices or bullets in your body you will not be able to undergo this procedure. 

There are no dietary restrictions.  However, it is advisable not to consume a full meal prior to the examination as this might make you feel uncomfortable during the procedure.  Avoid stimulants such as caffeine containing beverages.  Although not required, try to sleep during the procedure if at all possible.

Objects with magnetic strips such as credit cards may be damaged and are best kept at home or at least removed prior to the procedure.

How the procedure is performed?

After removing metallic items as described above, you will be asked to lie on a firm table and the area to be tested will be enclosed in a special coil after which the MRI technologist will slide the area to be examined into the center of the machine.  You will be instructed to relax and breathe regularly and not to move any part of your body since the slightest movement can degrade the quality of the images and make it difficult for the radiologist to give a correct and accurate interpretation of the images.  During the test you will hear several loud knocking or banging noises.  This is part of the normal operating procedure of the scanning process and you will be given ear plugs for your comfort. 

During the entire length of the procedure the MRI technologist will be able to continuously observe you from his/her console through a window with direct visual access.  An intercom system is also available and allows for two-way communication between you and the MRI technician.  An alarm button is usually placed in your hand which may be activated by a simple push should you experience any distress for whatever reason.  At the end of the procedure you may resume your normal duties.

Special circumstances

If you suffer from claustrophobia you must inform your physician.  A mild sedative administered orally may be prescribed 30 – 60 minutes prior to the procedure to help you relax.  If this does not work, you may need the sedative to be administered intravenously in which case you may be admitted to a same-day procedure unit.  In rare cases, the procedure may be performed under general anesthesia. 

 For infants and children, the procedure must be performed with intravenous sedation, and at times under general anesthesia, since they can not lie still.


  Neurological Tests

Electroencephalogram Brain wave test (EEG)
Nerve Conduction Studies (NCS) & Electromyography (EMG)
Evoked Potentials
Carotid Ultrasound
Computerized Axial Tomography (CT Scan / CAT Scan)
Magnetic Resonance Imaging (MRI)
Lumbar Puncture
© 2006 D M Kayed, MD, FAAN Dubai Neurology
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