What happens during an MRI procedure?
On the day, you will be asked to change into a gown (generally supplied to you) and to remove all things on your body that may affect the magnetic imaging (objects that will interfere with the powerful magnet). This includes jewellery, hairpins, eyeglasses, watches, wigs, dentures, hearing aids and underwire bras.
Depending on which area of the body is being examined, you will need to take off most or all your clothes and change into the supplied gown. If you are allowed to keep some clothing on, all pockets must be emptied (Fun fact: An MRI magnet can erase all information stored on the scanner strips of ATM bank cards).
The scan will usually be done by an MRI technologist and the images supplied to a radiologist for interpretation, your doctor will then explain the results to you once he/she has reviewed them. A technologist will monitor you from another room during the entire scan process (meaning you will be alone in the room during the scanning process).
The MRI machine will direct radio waves at your body and generate a strong magnetic field around you. The entire scanning process is painless and you cannot physically feel the radio waves or magnetic field. No parts of the scanning machine move around you.
During the scan, you will be requested to lie on your back on a table that is built in as part of the MRI scanner. You will be required to lie completely still for a period during the scan, with little or no movement. Some have straps which can be used on the head, arms and chest to assist you with remaining still.
The table will then slide into the space in the scanner that accommodates the magnet. A coil device will be placed over the area your MRI technologist would like to examine. A belt strap may also be wrapped around the area to ‘sense’ your breathing or heartbeat and trigger the machine to take a scan at an appropriate time.
If you have trouble keeping still or experience some degree of claustrophobia once inside the MRI magnet, you can be given a sedative to aid relaxation or you can request that mirror mounts be attached over your head so that you can see outside the MRI machine – this will significantly alleviate the feeling of claustrophobia. Alternatively, an open MRI machine may be an option if you have claustrophobia.
Once inside the scanner, you may feel some movement of air (or hear a fan) and slight vibrations. You may also hear a tapping noise as the MRI scan images are taken. Before sliding into the scanner that contains the magnet you may be given headphones with music or earplugs to counteract or reduce this noise.
You will be able to hear your MRI technologist during the test and may be asked to hold your breath for brief periods while a scan is taken. You can also talk to the technologist by microphone or intercom. It is very important to stay as still as possible throughout the scan process as movement can blur the images taken.
If you need contrast material, your technologist will administer it via an intravenous line (IV line) through a vein in your arm. You may feel some coolness as the material is administered. It can happen, although rarely, that some will feel a tingling sensation in the mouth (especially if you have dental fillings), warmth in the examined area of the body, nausea, vomiting, headache, pain, burning or trouble breathing, as well as dizziness. The material will be given over 1 to 2 minutes, followed by more scans.
During a fMRI (functional MRI) a few small tasks may be requested of you. You may be asked to tap your thumb against your fingers, answer a series of simple questions or rub a block of sandpaper. This may be done to pinpoint sections of your brain that typically control these types of functions.
An MRI can last anywhere from 15 minutes to more than an hour (sometimes 2 hours) depending on the purpose and areas being examined. If you haven’t been sedated, you are usually able to resume normal activities immediately after your scan.
Results and patient follow-up
A radiologist may discuss initial results of your MRI scan with you directly after the test. More thorough results are typically ready within a day or two after your scan and will be provided to your doctor or other specialist.
Sometimes your MRI results will be different from those of a CT scan, ultrasound or X-ray because it shows tissue differently. Your radiologist and specialist will carefully analyse any, and all tests conducted before making a diagnosis or drawing a conclusion.
From there he or he will discuss the findings in more detail with you, as well as any potential next steps which may be necessary.
Risk factors
The magnet is very powerful and may affect artificial limbs, artificial heart valves, implantable heart defibrillators, pacemakers and other medical devices what contain iron. There are no known serious effects as a result of the strong magnetic field used.
Any loose metal objects (such as a watch) can cause damage or injury of it is pulled toward the magnet during a scan. Any metal parts in or near the eyes can harm the retina. Irritation in the skin or the eye can occur due to iron pigments in tattoos or tattooed eyeliner.
There is a slight risk of an adverse reaction to the contrast material used (or an allergic reaction). This is typically mild and can easily be treated, so if you feel particularly strange after this has been administered, inform the person conducting the MRI immediately. Some may experience a slight risk of infection at the IV site.
If you are breastfeeding at the time of your MRI scan and need contrast material it is best to speak with your doctor or technologist beforehand to understand how it may affect your baby. A little dye may pass into breast milk and even less is believed to then be passed on to the baby while breast feeding. If you are nervous about this, you can store some of your breast milk ahead of your scan for use in the days thereafter.