A magnetic resonance imaging (MRI) scan is a painless procedure that lasts between 15 and 90 minutes, depending on the size of the area being scanned and the number of images being taken.
Before the scan
On the day of your MRI scan, you should be able to eat and drink and take any medication as usual.
However, if you are having an MRI scan of your bile ducts, you will usually be asked not to eat or drink anything for up to four hours before the scan. This type of MRI scan is known as magnetic resonance cholangiopancreatography (MRCP).
Due to the strong magnetic fields that are produced by the MRI scanner, it's important to remove any metal objects from your body, including:
- watches
- jewellery, such as earrings and necklaces
- piercings, such as ear, nipple and nose rings
- dentures (false teeth)
- hearing aids
- wigs (some wigs contain traces of metal)
Depending on which part of your body is being scanned, you may need to wear a hospital gown during the procedure. If you do not need to wear a gown, you should wear clothes without metal zips, fasteners, buttons, belts or buckles.
Some MRI scans involve having an injection of contrast dye. This makes certain tissues and blood vessels show up more clearly and with greater detail.
It's possible for contrast dye to cause tissue and organ damage in people with severe kidney disease. Therefore, if you have a history of kidney disease you may be given a blood test to determine how well your kidneys are functioning and whether it is safe to proceed with the scan.
An MRI scan is a painless procedure, so anaesthesia (painkilling medication) is not usually required. If you are claustrophobic, you could ask for a mild sedative to help you relax. If you would like a sedative, you should ask your GP or consultant well in advance of having the scan.
If you decide to have a sedative during the scan, you will need to arrange for a friend or family member to drive you home afterwards because you will be unable to drive for the first 24 hours (see below).
A general anaesthetic (medication that makes you unconscious) is often used when young children and babies have an MRI scan. This is because it is very important to stay still during the scan, which young children and babies are often unable to do when they are awake.
During the scan
An MRI scanner is a short tunnel that is open at both ends. You will lie on a motorised bed that is moved inside the scanner. You will enter the scanner either head first or feet first, depending on the part of your body being scanned.
A computer is used to operate the MRI scanner, which is located in a different room to keep it away from the magnetic field generated by the scanner.
The radiographer operates the computer, so they will also be in a separate room to you. However, you will be able to talk to them, usually through an intercom, and they will be able to see you at all times on a television monitor.
While you are having your scan, a friend or family member may be allowed to stay in the room with you. Children can usually have a parent with them. Anyone who stays with you will be asked whether they have a pacemaker or any other metal objects in their body. They will also have to follow the same guidelines regarding clothing and removing metallic objects.
To avoid the images being blurred, it is very important that you keep the part of your body being scanned still throughout the whole of the scan until the radiographer tells you to relax.
A single scan may take from a few seconds to three or four minutes. You may be asked to hold your breath during short scans. Depending on the size of the area being scanned and how many images are taken, the whole procedure will take between 15 and 90 minutes.
At certain times during the procedure, the MRI scanner will make loud tapping noises. This is the electric current in the scanner coils being turned on and off. You will be given earplugs or headphones to wear.
You'll be moved out of the scanner when your scan is over.
After the scan
An MRI scan is usually carried out as an outpatient procedure. This means that you will not need to stay in hospital overnight. After the scan, you can resume normal activities immediately.
However, if you have had a sedative, a friend or relative will need to take you home and stay with you for the first 24 hours. It's not safe to drive, operate heavy machinery or drink alcohol for 24 hours after having a sedative.
Your MRI scan will need to be studied by a radiologist (a doctor trained in interpreting scans and X-rays) and possibly discussed with other specialists. It is therefore unlikely that you will know the results of your scan immediately.
The radiologist will send a report to the doctor who arranged the scan, who will discuss the results with you. Unless they are needed urgently, it usually takes a week or two for the results of an MRI scan to come through.
