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.
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.
A special frame may be placed over the head for imaging in 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.
If your MRI scan is carried out privately, you may be sent home with a CD or DVD of the scan to give to your doctor.
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:
- Brain and spinal cord
- Bones and joints
- Heart and blood vessels
- Lungs and liver
People with conditions including the following may have an MRI scan:
- Brain tumours
- Dementia and Alzheimer's disease
- Parkinson's disease
- Multiple sclerosis (MS)
- Motor neurone disease (MND)
- Meningitis, encephalitis and other brain infections
- Brain or spinal cord injuries
- Bone and joint problems and injuries
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.