MRI scan – magnetic resonance imaging
What is an MRI scan?
An MRI (Magnetic Resonance Imaging) scanner uses magnetic fields, radio waves and a computer to take pictures of the inside of your body. It takes many pictures of a section (cross sections) of your body similar to a CT scanner, but does not use any radiation.
The MRI scanner has a short tunnel in the centre and a flat bed for you to lie on. When you are lying down, the bed will slowly move into the centre of the tunnel where the pictures are taken. This movement is controlled by MRI staff.
You may be given an injection of a special dye (contrast) into your veins.
Some of the things MRI scans are used to look at
A regular MRI is used to look at:
- the brain and spinal cord
- bones and joints
- the back
- liver and bile ducts.
MRI and angiography
MR angiography uses MRI to look at blood vessels in your brain, neck, heart, lungs, kidneys and legs.
MRI and venography
MR venography uses MRI to show blood flow in your veins.
MRI and arthrogram
An MR arthrogram uses MRI to look at your joints after a special liquid is injected into the joint.
Benefits of an MRI scan
- Very detailed diagnostic pictures of inside your head, body, legs, arms and joints.
- Generally painless.
- Does not use radiation.
- MR angiography and venography can show problems, including clots in your arteries and veins without using surgery.
Risks of an MRI scan
Your doctor knows the risks of having a MRI scan. Your doctor will consider the risks before recommending you to have a MRI scan.
An MRI scan is usually not recommended in early pregnancy.
You must tell staff if you have:
- a pacemaker
- a cochlear implant
- a spinal stimulator
- metal implants, including aneurysm clips, other surgical clips or staples, metal rods or pins in your bones, or false teeth
- any pieces of metal in your eyes
- kidney disease.
The presence of these objects may add to the risks of having an MRI Scan and may cause it to be cancelled.
If you are having dye, there is a very small risk of:
- an allergic reaction (usually mild and easily controlled by medication)
- infection at the site of an injection.
If you are at all concerned regarding the risks, talk to your doctor before the examination.
- Bring your referral letter or request form and all X-rays taken in the last 2 years with you.
- Leave the X-rays with the radiology staff as the doctor may need to look at them. The MRI staff will tell you when these are ready to be picked up.
- Wear comfortable, loose clothing.
- Leave all jewellery and valuables at home. Metal objects, such as watches, keys, coins and jewellery cannot be taken into the MRI room. Cards with magnetic strips such as bank cards will be erased by most MRI scanners.
If you are having dye:
- You may be asked not to eat or drink for a few hours before the MRI scan.
Tell your doctor before the scan
- If you are or may be pregnant.
- If you don’t like closed in spaces (claustrophobic). Your doctor may then discuss the possibility of you being given something to relax you just before the scan (sedative). If the doctor has decided you need a sedative and written it on the request form, you will need to let the staff know when you book your scan.
- If you are having dye tell the staff about any medical conditions you have, including kidney disease, allergies and asthma (some conditions such as kidney disease may mean you cannot have an MRI with dye).
Just before the scan
- You may be given a gown to wear.
- You may be asked to remove any metal objects.
- You may be given a sedative if you don’t like closed in spaces (claustrophobic).
What happens during an MRI scan
The staff will ask you to lie on the bed, and will place a receiver around the part of your body being scanned. Straps or pillows may be used to help you keep still during the scan; however you will be able to remain comfortable.
If you are having dye or sedative injected, MRI staff will put a needle into a vein in your hand or arm.
Possible side effects of dye:
- You may feel a slight coolness and a flushing for a few seconds.
- Part of your body may feel warm – if this bothers you, tell the staff.
The MRI machine makes a lot of noise during the scan, which may sound like thumping or humming. You will be given earplugs or headphones to block out the noise or listen to music. (In most MRI centres you can bring your own CD to listen to.)
The staff will leave the room where they can control the movement of the bed from behind a screen. They can see, hear and speak to you at all times. You will be able to speak to them at all times. They will tell you what is happening, when to hold still and if you need to take a deep breath and hold it. If you get stiff, need to move or are feeling closed in (claustrophobic), tell the staff.
The MRI staff will use a remote control to slowly move you into the tunnel of the MRI scanner.
When the scanning is finished you will be asked to wait while the staff check the pictures.
The scan takes between 30 minutes and an hour, including time taken to get you ready.
You have the right to refuse an examination and may do so if you wish. You may be asked to complete a consent form.
When will I get the results?
The amount of time it takes for you to get your results will differ depending on where you get your scans done. The radiology doctor will look at the pictures and write a report. The pictures may be on films or on a CD.
Ask whether you should wait to take the pictures and report with you, or whether they will be sent to your doctor.
Your doctor will need to discuss the report with you. You will need to make an appointment to do this.
After an MRI scan
You will be able to go soon after the MRI is finished and can continue with normal activities.
If you had dye:
- Staff will need to take out the needle if it is still in your arm.
- Staff will give you any special instructions.
- The dye will pass out of your body in your urine. You will not notice it as it is colourless.
- Drink plenty of fluid to help get rid of the dye.
If you had a sedative
- Staff will need to take out the needle if it is still in your arm.
- You must not drive a car or take public transport for 24 hours afterwards.
- You must have someone with you for 24 hours afterwards.
- You must not operate machinery for the rest of the day.
Costs of an MRI scan
For an Australian patient in a public hospital in Western Australia:
- public patient – no cost to you unless advised otherwise
- private patient – costs can be claimed through Medicare and your health insurance provider
For a patient in a private hospital or private imaging site in Western Australia – ask your doctor or the staff where you are having your test done.
This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.