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Magnetic Resonance Imaging (MRI)


Magnetic resonance imaging (MRI) is a painless, non-invasive diagnostic imaging technology that uses a strong magnetic field and radio frequency waves to produce images. The scanner creates a magnetic field and sends radio frequency pulses through the body tissues. The tissue response is then measured and an image is created from this information.

MRI scans can provide information about the brain, spine, joints, organs and vessels. MRI can also illustrate differences in tissues that may not be visible with other imaging modalities. Some MR examinations require an injection of Gadolinium to visualize structures more clearly. Gadolinium has a paramagnetic property that makes it appear bright within a magnetic field. It can be helpful in demonstrating vascular structures within tissues.

If you suffer from claustrophobia you may need medication called “sedation” before the MRI to keep you relaxed.  Please note that you will need to ask your health care provider for this medication and bring it with you to take before your MRI. We do not provide sedation in our department.  If you are given sedation, you must be driven home by another adult as you are not to drive after taking sedatives

Who We Help

Our Pregnancy Policy

There have been no reported adverse effects demonstrated in pregnant women or the fetus; however the FDA guidelines suggest that MRI be used during pregnancy only when there are clear medical indications. Our policy is to avoid an MRI unless requested by a Neurosurgeon or Neurologist and a consent form must be signed with a Radiologist.

Contact Information

To book or follow up on the status of your appointment, please contact:
Mississauga Hospital
Phone: 905-848-7554
Fax: 905-848-7295

Credit Valley Hospital
Phone: 905-813-4179
Fax: 905-813-4172

A completed and signed referral must be submitted by your health care provider prior to us booking an appointment for an MRI scan.


  1. All MRI requisitions must be fully completed with the following:
    • patient's full name and date of birth,
    • area of interest to be scanned
    • appropriate clinical information
  2. All MRI requests must include a completed MRI Information & Screening Form. It is important that the patient both completes and signs this form. All previous surgical information must be recorded on the form. Operative reports may be requested to ensure patient safety prior to the booking of an appointment. An MRI may be contraindicated if the patient has surgically implanted devices.
  3. Any patients with a history of exposure to metal fragments in or around the eyes, or exposure to metal dust in the workplace (i.e. welders, metal workers), will require a pre MRI orbital x-ray to ensure there are no metallic foreign objects within the orbit.
  4. If a patient suffers from claustrophobia and requires sedation prior to the MRI, the ordering physician must arrange a prescription for the patient prior to their MRI exam. The MRI department does not provide sedation. If a patient is prescribed sedation they must be accompanied home by another adult. The patient may not drive home after the sedation.

Resources for Patients & Their Families

How to Prepare for Your Procedure

If You are Having an Abdominal and Pelvic Exam   
Do not eat or drink anything for 4 hrs before your appointment
Medications can be taken with a small amount of water

If You are Having a Cardiac Exam
No Caffeine the morning of the exam.
Do not eat or drink anything for 2 hrs before your appointment

If You are Having a Brain or Spine/Extremity Exam
No preparation is required

Arriving for your Exam:
After you register in Diagnostic Imaging you will be asked to sit in the MRI waiting room.

An MRI technologist will explain the procedure to you and confirm the information provided on the screening form. It is advised that if you plan on taking sedation, that it is taken after you have registered in Diagnostic Imaging. If you are taking sedation, please be sure to have an adult accompany you home.
Once the procedure has been explained you will be instructed to change into a hospital gown. Lockers are available to lock up your belongings and valuables.

When it is time for your exam a technologist will escort you into the room.

During the Exam:
After the exam has been explained to you the technologist will provide you with hearing protection. This protection will help reduce the loud thumping sounds which are produced during the scan.
The MR scanner is a large tube-shaped magnet with a padded table that moves into the centre of the magnet. The body part being examined will determine if you go into the scanner head or feet first, as well as how far you go in. In most cases equipment called surface coils will be placed on the area we are scanning.
The technologist will give you an Emergency call bell to squeeze if you need to get their attention.

It is very important that you remain relaxed and very still during the exam. Movement can cause non-diagnostic images and they will need to be repeated. In some abdominal exams we may ask you to hold your breath for up to 20 seconds while the pictures are taken.

Most exams will take between 30-45 minutes, however there are some that can take up to an hour. Please allow for enough time in your day to accommodate your MRI exam.

Some exams require an injection of contrast media called gadolinium. It is a colorless fluid that is injected into a vein in your arm. Gadolinium is very safe and the risks will be discussed with you by the technologist. If contrast is required it is important that you remain very still as the images before the injection must match the images obtained after the injection.

What to Expect From Your Procedure

How It Works

Your body is composed of small particles called atoms. Most of the body is composed of Hydrogen atoms that under normal circumstances spin around at random. However, when you are placed within a strong magnetic field, the hydrogen atoms line up and spin in the same direction as the magnetic field. When a radio frequency wave is transmitted through the tissues in the body the Hydrogen atoms produce a signal. These signals are measured to produce an image.

While it is working the scanner creates a noise. This noise is the electrical current rising within the wires of the gradient magnet. The current in the wires are opposing the main magnet field; the stronger the field the louder the gradient noise.

Getting Your Results

Once your MRI is completed it will be reviewed by a radiologist and the report will be available to your ordering physician within about 2 weeks.