How an MRI scan is performed

A magnetic resonance imaging (MRI) scan is a painless procedure that lasts 15to 90 minutes, d epending on the size of the area being scanned and the number ofimages being taken .

Before the scan

On the day of your MRI scan, you should be able to eat, drink and take any medication as usual, unless advised otherwise.

In some cases, you may be asked not to eat or drink anything forup to four hours before the scan, and sometimesyou may be asked to drink a fairly large amount of water beforehand. This depends on the area being scanned.

When you arrive at the hospital, you'll usuallybe asked to fillin a questionnaire about your health and medical history. This helps the medical staff to ensure you have the scan safely.If you do not need to wear a gown, you should wear clothes without metal zips, fasteners, buttons, underwire (bras), belts or buckles.

Contrast dye

Some MRI scans involve havingan injection of contrast dye. This makes certain tissues and blood vessels show up more clearly andin greater detail.

It's possible for contrastdye to cause tissue and organ damage in people with severe Chronic kidney disease . If you have a history of kidney disease, you maybe given a blood test todetermine how well your kidneys are functioning and whether it's safe to proceed with the scan.

You should also let the staff know if you have a history of allergic reactions or any blood clotting problems before having the injection.

Anaesthesia and sedatives

An MRI scan is a painless procedure, so anaesthesia (painkilling medication) isn't usually required. If you're claustrophobic, you canask fora mild sedative to help you relax you shouldask your GP or consultant well in advance of having the scan.

If you decide to have asedative during the scan, you'll need to arrange for a friend or family member to drive you home afterwards, as you won't be able to drive for 24 hours.

General anaesthetic is often used when young children andbabies havean MRI scan. This is becauseit's very important to stay still during the scan, which young children and babiesare often unable to do when they're awake.

During the scan

An MRI scanner is a shortcylinder that's open at both ends. You'll lie on a motorised bed that's moved inside the scanner. You'll enterthe scanner either head firstor feet first, depending on the part of your body being scanned.

In some cases, a frame may be placed over the body part being scanned, such as the head or chest. This frame contains receiversthat pick up the signals sent out by your body during the scan and it can helpto create a better-quality image.

A computerisused to operate the MRI scanner, which is located in a different roomto keep itaway from the magnetic field generated by the scanner.

The radiographer operates the computer, so they'll also be in a separate room to you. However, you'll be able to talk to them, usually through an intercom, and they'll be able to see you at all times on a television monitor.

While you're havingyour 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 apacemakeror any othermetal objects in their body. They'll also have to follow the same guidelines regardingclothing and removing metallic objects.

To avoid the images being blurred, it's very important to 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 tothree 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 15 to 90 minutes.

The MRI scanner will make loud tapping noises at certain times during the procedure. This is the electric current in the scanner coils being turned on and off. You'll be given earplugs or headphones to wear.

You're usuallyable to listen to music through headphones during the scan if you want to, and in some cases you can bringyour own CD.

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 you won't need to stay in hospital overnight. After the scan, you can resume normal activities immediately.

However, if you've 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 needs to be studied by a radiologist (a doctor trained in interpreting scans and X-rays) and possibly discussed with other specialists.This means it'sunlikely you'll 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. It usually takes a week or two for the results of an MRI scan to come through, unless they're needed urgently.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 29 Nov 2016