What Is an MRI?

MRI stands for Magnetic Resonance Imaging. It's a medical imaging technique that uses a strong magnetic field and radio waves to create detailed images of the inside of your body — including soft tissues, organs, and bones. Unlike X-rays or CT scans, MRI does not use ionizing radiation.

Doctors order MRIs to investigate a wide range of conditions, including joint and spine problems, brain abnormalities, tumors, heart conditions, and internal organ issues.

How Does an MRI Machine Work?

The MRI machine is essentially a large, tube-shaped magnet. When you lie inside it, the magnetic field temporarily aligns hydrogen atoms in your body. Radio waves are then used to knock these atoms out of alignment, and as they realign, they emit signals that the scanner detects and converts into detailed images.

The process is entirely painless. The machine makes no physical contact with you beyond positioning, though it does produce loud clicking and knocking sounds during the scan.

Before the Scan: How to Prepare

Your radiology team will give you specific instructions beforehand, but here are the general steps:

  • Remove all metal objects — jewellery, piercings, hairpins, watches, and hearing aids must all come off.
  • Inform staff of any implants — pacemakers, cochlear implants, metal plates, screws, or clips may be affected by the magnetic field. Always disclose these.
  • Fasting may be required — depending on which part of the body is being scanned and whether contrast dye is used.
  • Wear comfortable clothing — you may be asked to change into a hospital gown.
  • Inform staff of claustrophobia — if you're anxious about enclosed spaces, tell the team in advance. Sedation or an open MRI may be available.

Step-by-Step: What Happens During the Scan

  1. Check-in and screening: You'll complete a safety questionnaire about implants, medications, and allergies.
  2. Preparation: You'll change into a gown and remove all metal. If contrast dye is being used, a small IV will be placed in your arm.
  3. Positioning: You'll lie on a padded table that slides into the MRI machine. Depending on the scan, different coils (receiver devices) may be placed around the area being scanned.
  4. The scan itself: You must lie still. The machine will make loud rhythmic noises — banging, clicking, and humming. You'll be given earplugs or headphones. The scan typically takes between 20 and 60 minutes.
  5. Communication: You'll have a call button in your hand to alert the radiographer at any time. They can see and hear you throughout the scan.
  6. After the scan: Unless you've received sedation, you can usually go home or return to your ward immediately. A radiologist will analyze the images and send a report to your doctor.

What Does Contrast Dye Do?

Some MRI scans use a contrast agent (usually gadolinium-based) injected through the IV. This dye helps certain structures show up more clearly on the images — particularly blood vessels, tumors, and areas of inflammation. You may feel a brief cool sensation as it's injected. Allergic reactions are rare but the team will monitor you if contrast is used.

Is an MRI Safe?

For most people, MRI is very safe. There is no radiation involved. The main considerations are:

  • Metal implants: Certain implants can be unsafe in a strong magnetic field. Always disclose your full medical history.
  • Pregnancy: MRI is generally avoided in the first trimester unless the clinical benefit outweighs any potential risk. Always tell the team if you are or might be pregnant.
  • Kidney function: If contrast dye is used, good kidney function is typically required to clear it safely from the body.

If you have concerns about your upcoming MRI, speak with your doctor or the radiology team. The more information you have, the more comfortable and confident you can feel going in.