MRI Scan: Definition, Purpose, Safety, Side Effects

What is an MRI?

MRI - or magnetic resonance imaging - is one of the newest medical imaging and safest techniques. Reliable and precise, it provides two-dimensional and three-dimensional views of the inside of the body. It is particularly useful for detecting diseases or internal disorders that conventional examinations have failed to identify.

Today, an MRI can be used to observe various tissues: organs such as the heart or the brain, and also muscles and tumours for which it will provide a very fine analysis. The fields of application are wide, and an MRI can be performed to explore cerebral, spinal, cardiac, digestive, gynecological, vascular, and joint pathologies.

How Does an MRI Work?

An MRI provides slice images of the body. Unlike a traditional scanner that uses X-rays, magnetic resonance images are the result of the interaction between a magnetic field created by the machine and the hydrogen atoms in the patient's body.

The MRI device is equipped with a very powerful magnet that sends waves that will vibrate the hydrogen nuclei contained in the organic tissues. The return of these hydrogen nuclei to their state of equilibrium will cause the formation of a signal in a receiving antenna. These are the changes that will be used to create the images on the screen.

How is an MRI Done?

An MRI exam usually lasts 15 to 30 minutes. However, the duration can take up to one hour for a more thorough examination. After removing their clothing, the patient will lie on a bed. The device is placed on the area that is to be examined, and then the bed will slide gently into the mini tunnel. It is inside the mini tunnel that the magnetic field is produced.

During the examination, the patient must remain perfectly still but has a bell at their disposal to alert the examiner if something is not right. The examination is completely painless and non-invasive. The only drawback is the noise of the machine, and the feeling of confinement that can make some patients uneasy. Once the images are taken, they will be interpreted by a radiologist.

Safety: Are There Any Risks Associated with an MRI Exam?

An MRI examination is completely painless and poses no risk to the patient. The patient must, however, remove all metal objects (watches, belt, jewelry, etc.) prior to undergoing the exam. They must also inform the doctor about the use of a heart-shaped battery, valve, or prosthesis that could interfere with the examination and put the patient at risk.

While it's well-tolerated in general, an MRI can sometimes cause mild allergic reactions (urticaria). More serious reactions can be anticipated during a prior consultation. Those suffering from claustrophobia may also experience discomfort during the procedure, however this is usually manageable with the help of a radiologist. Whilst effective, MRI is usually not recommended during pregnancy.

MRI: What are the Drawbacks?

Due to the strong magnetic field, some factors may be contraindications to an MRI. This could be the presence of medical devices or metals in the body that could move (pacemaker, heart valves, vascular clips, prostheses, etc.) The condition of the patient can also be a source of contraindications, for example, if they are unable to lie down or remain still.