Boots WebMD Partners in Health
Return To Boots

What is an MRI scan?

Magnetic resonance imaging (MRI) is one of the tools doctors have to help diagnose and monitor conditions affecting internal organs, tissue and bone.

How MRI works

Strong magnetic fields and radio waves are used to form detailed images of the body a tiny 'slice' at a time.

Magnetic waves bounce off tiny protons in the water molecules that make up the body. The signals received from millions of protons build-up to form the scanning image.

The images can then be viewed as a 3-D view of a person's insides.

mri_scan_medref.jpg

What to expect during an MRI

An MRI scan is usually carried out as a day patient procedure. After the scan, you can go back to your normal daily activities.

Before the magnetic scan, you will be asked to remove anything containing metal. This includes watches, jewellery, piercings, dentures, hearing aids and some wigs.

You will probably have to wear a hospital gown.

For some MRI scans, an injection of contrast dye is needed first to help show details more clearly.

A radiographer will ask a person to lie flat and still on a bed that then goes inside a tube of magnets. You may go in head or feet first.

MRI scanner

A special frame may be placed over the head for imaging of the brain and skull.

The radiographer will operate the scanner from a control room and you can talk to them over an intercom.

Scans may take as long as 90 minutes but some may be as quick as 15 minutes depending on what part of you is being scanned and how many images are required.

The machine can be noisy, sounding like loud hammering going on inside the scanner as it does its work. Headphones or earplugs will usually be provided.

You are unlikely to get the results of the scan straight away, as the results will need to be assessed by a consultant.

Uses of MRI tests

Almost any part of the body can be scanned with an MRI. MRI scans are often requested by doctors to look at:

People with conditions including the following may have an MRI scan:

MRI scans may be used to help diagnose breast cancer but are not needed in all cases following a mammogram. An MRI scan may be used to check breast implants, such as the faulty PIP implants.

Who shouldn't have an MRI

People who are claustrophobic - anxiety over being in enclosed spaces - may have concerns over going into an MRI tube. Open MRI machines where you are not closed-in on all sides may be available as an alternative for people with these concerns. 

A sedative may be offered to help calm someone's fears. If this is taken, you will not be able to drive yourself home afterwards.

Children and babies may be given a general anaesthetic to make sure they are completely still for the scan.

The use of magnets means MRI scans are not suitable for people with implants such as pacemakers for heart conditions, implanted pain devices and cochlea implant for hearing conditions.

Artificial joints, medical clips left inside the body after operation - for example to seal blood vessels - will also rule out an MRI, as will an intrauterine device (IUD) or contraceptive coil.

There is no evidence that MRI scans are a risk for pregnant women. However, as a precaution, the NHS does not usually recommend MRI scans during the first trimester (three months) of pregnancy.

WebMD Medical Reference

Stay informed

Sign up for BootsWebMD's free newsletters.
Sign Up Now!

Popular slideshows & tools on BootsWebMD

woman_holding_head_in_pain
How to help headache pain
rash on skin
Top eczema triggers to avoid
79x79_causes_of_fatigue_and_how_to_fight_it.jpg
Causes of fatigue & how to fight it
period_questions_answered
Tips to support digestive health
woman looking at pregnancy test
Is your body ready for pregnancy?
woman sleeping
Sleep better tonight
girl_sneezing_into_tissue
Treating your child's cold or fever
bucket with cleaning supplies in it
Cleaning and organising tips
adult man contemplating
When illness makes it hard to eat
woman holding stomach
Understand this common condition
cold sore
What you need to know