MRI doesn't cause pain or discomfort.
A person having an MRI scan
DiagnosisMRI is the best scan available for most conditions and can be used to investigate the entire body. It can be used for:
- spinal, joint, ligament or tendon problems
- measuring blood flow in blood vessels
- diagnosing and planning of treatment for cancer
- gynaecological problems
- breast disease
- assessment of brain function after a stroke
- assessment of heart function
Is MRI suitable for you?Not everyone can have an MRI scan. The magnetic field from the scan affects some metals. It's important to tell your radiographer (a health professional trained to perform MRI procedures) if you have a medical device implanted in your body. Examples include:
- heart pacemaker
- heart defibrillator (a device to establish a regular heart rhythm)
- heart valve
- medicine infusion pump (such as an insulin pump)
- inner ear implant (a hearing aid)
- neurostimulator (a device that stimulates nerves)
- aneurysm clip (a metal clip on an artery)
- shunts (tubes) in the brain
- joint replacements/large metal implants
- stents (tubes) in the heart or arteries
- eye, penis, or breast implants
- an intra-uterine contraceptive device or coil
- shrapnel or gunshot wounds
- body piercing
- metal fragments anywhere in your body
- tattoos or transdermal patches
If you're pregnant
MRI scans aren't usually done on pregnant women, but can be done after the first three months of pregnancy if absolutely necessary. If you think you are or could be pregnant, tell your radiographer before your MRI appointment.
What are the alternatives?Depending on your circumstances, alternative procedures that can be used to make images of the inside of your body include X-ray, ultrasound or computerised tomography (CT) scan.
Your doctor will advise you on the best examination for you if MRI is unsuitable.
Preparing for your MRI scanMost MRI scans don't need any special preparation. However, if you're having an abdominal or pelvic scan, you may be asked to follow special instructions about eating and drinking.
Some types of metal can interfere with the scan. Therefore, it's best to wear clothing that doesn't have metal zips, buttons, clasps or underwiring (such as bras).
An MRI scan is usually performed as an out-patient procedure in a hospital. This means that you can have the scan and go home the same day.
At the hospital, your radiographer will ask you to complete and sign a safety questionnaire.
If you are anxious or have claustrophobia, you may be offered a sedative to help you relax during the scan. Young children may also be offered a sedative or a general anaesthetic. This means they will be drowsy/asleep during the procedure.
Your radiographer may ask you to take off your clothes and put on a hospital gown.
Your radiographer will ask you to remove metal objects such as hair clips, hearing aids, jewellery, glasses, dentures with metal components, your mobile phone and wrist watch. He or she will also ask you to leave behind coins, keys and your credit cards, and remove all make up.
Relatives or friends who wish to accompany you into the MRI room also need to follow these guidelines, and complete and sign a safety questionnaire.
Contrast medium (dye)A dye may be used to make some tissues show up more clearly. If needed, the dye is injected into a vein in your hand or arm. The dye is harmlessly removed from your blood by your kidneys and is passed out in your urine.
A very small number of patients may be allergic to the dye. Tell your radiographer if you have any allergies. If you have poor kidney function you may need to have a test before having the dye injected.
About the procedureThe scan can take between 30 minutes and an hour and a half, depending on the specific examination.
You will lie on your back on a movable table, which slides inside the cylinder shaped scanner. Generally the part of your body being examined is placed in the middle of the scanner. The scanner is open ended so you won't be completely enclosed at any time.
Your radiographer will operate the scanner from behind a window, and will be able to see and hear you during the scan. You will be given an alarm call button to hold during the scan, which you can press to get your radiographer's attention.
It can take several minutes for each image to be taken, and it's important to lie very still and breathe gently during the process. Your radiographer may ask you to hold your breath at certain times during the scan.
The machine is noisy and will make loud knocking or buzzing sounds throughout the scan, so you will have to wear earplugs or headphones.
When the scan is complete, the table will be removed from the scanner.
What to expect afterwardsYou will usually be able to go home straight after the scan.
Sedation temporarily affects your co-ordination and reasoning skills, so you mustn't drive, drink alcohol, operate machinery or sign legal documents for 24 hours afterwards. If you're in any doubt about driving always follow your doctor's advice, and please contact your motor insurer so that you're aware of their recommendations. This means if you had a sedative, you will need to arrange for someone to drive you home. You should try to have a friend or relative stay with you for the first 24 hours.
If you have had a dye injection, it's a good idea to drink plenty of water for the next 24 hours to help flush the dye out of your body.
Your radiologist (a doctor specialising in MRI, CT and X-ray methods to diagnose medical conditions) will examine your MRI scans and send the results to the doctor who requested your test.