MRI

MRI (Magnetic Resonance Imaging) is a scan that uses a strong magnetic field and radio waves to create detailed pictures of the inside of your body — without using X-ray radiation.

During the scan, the magnetic field causes hydrogen atoms in your body's water molecules to line up. Radio waves are then briefly applied, and as the atoms return to their original position, they release tiny signals. A computer collects these signals and turns them into cross-sectional images — like very precise slices — of whichever part of the body is being examined. This gives doctors a clear view of soft tissues such as the brain, muscles, ligaments (the bands that connect bones), and organs, which standard X-rays cannot show well.

Doctors request an MRI when they need a detailed image of soft tissues, joints, organs, or the nervous system (the brain and spinal cord) that other scans cannot provide clearly enough. It is used both to detect a problem for the first time and to monitor a known condition over time.

• Brain and spinal cord conditions — tumours, stroke (when blood flow to the brain is blocked or a blood vessel bursts), multiple sclerosis (a disease where the body's immune system attacks the nerves), and injuries
• Joint and bone problems — torn ligaments or cartilage (the cushioning tissue in joints), herniated discs (slipped spinal discs), and bone infections
• Heart and blood vessel assessment — structural heart problems, blocked or narrowed arteries
• Abdominal and pelvic organs — liver disease, kidney tumours, uterine (womb) and ovarian conditions
• Breast imaging — particularly when mammography results are unclear or for high-risk patients
• Cancer staging and treatment monitoring — to see whether a tumour has spread or is responding to treatment
• Unexplained pain, numbness, or weakness in any part of the body when the cause is not yet clear

An MRI is not suitable for everyone. Your doctor will assess whether it is safe for you if any of the following apply.

• Certain metal implants inside the body — such as a pacemaker (a device that regulates the heartbeat), cochlear implant (hearing device), or some older types of aneurysm clip (a clip placed on a blood vessel in the brain), because the strong magnet can interfere with or move them
• Metal fragments in the eyes or body from a past injury or occupation
• Severe claustrophobia (intense fear of enclosed spaces) — though open MRI machines or sedation may be offered as alternatives
• First trimester of pregnancy — usually avoided as a precaution, though MRI is generally considered safer than X-ray during pregnancy

MRI does not use ionising radiation (the type used in X-rays), so it carries no radiation risk; for most people it is a very safe procedure, but a small number of specific risks are worth knowing about.

• Allergic reaction to contrast dye — some MRI scans use a contrast agent (a dye injected into a vein to make certain structures more visible); mild reactions such as itching or rash are uncommon, and severe reactions are rare
• Nephrogenic systemic fibrosis (scarring of skin and organs) — a very rare complication linked to contrast dye in patients who already have severely reduced kidney function
• Movement or heating of metal implants — the magnetic field can interact with certain metallic devices or fragments inside the body, which is why a thorough safety check is done beforehand
• Claustrophobia or anxiety — the scanner is a narrow tunnel and some patients feel anxious or uncomfortable inside it
• Loud noise — the machine produces repetitive banging sounds that can be startling; ear protection is provided
• No risk for the vast majority of patients who have no metal implants and do not require contrast dye

Preparation for an MRI is generally straightforward. Whether fasting is required depends on the type of scan and whether contrast dye will be used — your doctor or the radiology team will give you specific instructions. For most brain, joint, or spine MRIs, you can eat and drink normally beforehand. For abdominal or pelvic scans, you may be asked to fast for a few hours.

If you take regular medications, in most cases you can continue them as normal unless the radiology team advises otherwise. If contrast dye will be used, blood tests to check kidney function are usually done first, especially for patients with diabetes or existing kidney problems. Tell the team about any allergies — particularly to iodine or previous contrast agents — and about all medications including blood thinners, as these may sometimes need to be paused.

Before entering the scan room, you will be asked to remove or leave behind all metal objects, because even small items can be dangerous near the powerful magnet. This includes:

• Jewellery, watches, hairpins, and piercings
• Glasses and hearing aids
• Dentures with metal components
• Keys, coins, and credit or bank cards (the magnetic strip will be erased)
• Any clothing with metal zips, underwire, or clasps — you may be given a hospital gown to wear

You will also complete a safety questionnaire asking about implants, previous surgeries, tattoos (some older tattoo inks contain metal), and occupational exposure to metal. Be thorough and honest — this protects your safety.

Here is what typically happens during the procedure itself:

• You lie down on a padded table that slides into the centre of the MRI machine.
• A coil (a frame-like device that improves signal quality) may be placed over or around the body part being scanned.
• If contrast dye is needed, a small cannula (thin flexible tube) is inserted into a vein in your arm before or during the scan.
• The table moves you into the tunnel. The team leaves the room but can see and hear you at all times through a window and intercom.
• You are given ear protection because the machine makes loud knocking sounds throughout the scan.
• You will be asked to lie as still as possible. Movement blurs the images.
• The scan runs for as little as fifteen minutes for a single body part, or longer if multiple areas or detailed sequences are needed — your team will give you an estimate.
• When the scan is finished, the table slides out and you can get up.

For the vast majority of patients, an MRI requires no recovery time at all — you can return to your normal activities, including driving, eating, and working, as soon as the scan is complete. If sedation was given to help with anxiety or claustrophobia, you will need to rest in the facility until the sedative has worn off and will need someone to take you home. If contrast dye was used, drinking plenty of water afterwards helps your kidneys clear it from the body.

• No physical restrictions apply after a standard MRI without sedation.
• If sedated, avoid driving or operating machinery for the rest of that day.
• No wound care is needed — the scan is completely non-invasive (nothing enters or cuts the skin) unless a contrast injection was given, in which case the small needle site may be lightly pressed for a moment.
• Results are not given immediately. A radiologist (a doctor who specialises in reading medical images) will analyse the images and send a report to your referring doctor, who will then discuss the findings with you — this can take anywhere from hours to several days depending on the hospital.
• Follow-up appointments, further scans, or referrals to a specialist will be arranged by your doctor based on what the MRI shows.
• If you had contrast dye and notice redness, swelling, or itching at the injection site — or any unusual symptoms such as difficulty breathing — contact the medical team promptly.