What is an MRI Scan and how does it work?
An MRI (Magnetic Resonance Imaging) scan can be used to
examine almost any part of the body, such as the brain, spine, bones
and joints. It can also be used to scan the heart, blood vessels,
breasts and all of your internal organs.
The results of an MRI scan can be used to help diagnose conditions,
plan treatments and assess how effective previous, treatment has
been.
An MRI scanner is a large tube that contains powerful magnets. You
lie inside the tube during the scan.
The human body is made up of water molecules, consisting of
hydrogen and oxygen atoms.
At the centre of each hydrogen atom is a smaller particle called
a proton. Protons are like tiny magnets and are very sensitive to
magnetic fields.
When you lie under powerful scanner magnets, the protons in your
body line up in the same direction, in the same way a magnet can
pull the needle of a compass.
Short bursts of radio waves are sent to areas of the body, knocking
the protons out of alignment. When the radio waves are turned off,
protons realign. This sends out radio signals, which are picked up by
receivers. These signals provide information about the exact location
of protons in the body. They also help to distinguish between various
types of tissues in the body, because different tissue types realign at
different speeds and produce distinct signals.
The signals from the millions of protons in the body are combined to
create detailed images of the body.
How is the Scan done?
During the scan you will be asked to lie on a table which moves
inside a large tubular machine.
The inside of the scanner is well lit and has a fan which gently blows
fresh air over you.
The Radiographer who performs the scan will be able to see you at
all times and will talk to you through an intercom. You will be given a
buzzer to use if you need to alert staff during the scan.
It is very important that you are comfortable and remain very still
as even slight movement can spoil the images and reduce their
usefulness. Staff will do their best to make you feel relaxed and
therefore ensure the best possible pictures are obtained.
You will hear very loud banging noises while the scanner is taking
pictures – this is normal. You will be given ear plugs to dull the
banging noise and protect your hearing as well as headphones
so you can hear the Radiographer. Music can be played to you
(depending on the type of scan you are having).
When the scan is over the table is moved back out from the scanner.
Will I feel any pain/discomfort during the scan?
There are many ways in which the staff can help to alleviate these
fears by adapting techniques and using prism mirrors or eye masks.
If you feel you may struggle with the scan then perhaps a
conversation with the referring consultant may be necessary or a
phone call with the radiographers in the scan room that may be able
to talk you through the scan.
How long does it take?
Most MRI scans take between 15 and 60 minutes. Please allow
enough time for your appointment and parking.
How do I prepare for the scan?
MRI scans are routinely performed as an outpatient procedure. You
can eat and drink normally before the scan, UNLESS you have been
instructed otherwise.
It is very important not to bring any metal into the scan room without
letting the radiographer know. Before the scan you will be asked to
change into a hospital gown and to remove your watch, keys, coins
and credit cards. These can all be damaged by the strong magnet
of the MRI scanner, or might cause distortions in the MRI pictures.
A locker and basket will be provided for your valuables and clothing,
although you are strongly advised to leave jewellery / valuables at
home.
When you arrive at MRI you will be asked a series of safety
questions to find out if you have any metal or implants in your body.
For some MRI scans we need to measure your heart beat by placing
small dots and wires on your back or chest. Some MRI scans require
an injection of a ‘dye’ agent (contrast agent – gadolinium). The risks
associated with the ‘dye’ are very small but the Radiographer will
discuss this further on the day, if an injection is required.
What are the benefits of having an MRI Scan?
MRI scans are performed without the use of radiation. They often
provide a more detailed image than other scans and are more
effective at showing up the differences between various types of
tissue. The high quality images can help your doctor to diagnose
certain conditions and determine the best treatment options.
Who can have an MRI Scan?
Not everyone can have an MRI scan.
It may not be possible or safe to have an MRI scan if you have any of the following:
• Cardiac pacemaker or ICD (Implantable Cardiac Device).
• Loop Recorder.
• Surgical clips in your head (particularly aneurysm clips).
• Some artificial heart valves.
• Electronic stimulators (e.g. spinal).
• Implanted pump or recorder.
• Internal metal.
• Surgery in last 2 months.
• ‘Silver backed’ dressings.
• You are or might be pregnant.
If you think any of the above applies to yourself then please contact the MRI department immediately: 01253 956789.
It is very important to inform staff about previous surgery or
metal implants as you may not be suitable for an MRI scan.
Are there any risks involved?
Any risks involved in the procedure will be discussed in more detail
before the scan and / or before you sign a consent form.
Are there any alternatives?
The doctor feels an MRI scan to be the best examination
for you.
You can ask your doctor during your clinic appointment to discuss
alternative tests or procedures.
When can I resume normal activities?
You may resume normal activities as soon as the scan is over.
When do I get the results?
No results will be given on the day of the MRI scan. The images will
studied by a radiologist or reporting radiographer (professionals who
specialise in interpreting images) who will produce a report of the
results, which will be made available to the clinician who requested
the scan.
Additional Information
Relatives and Escorts
You may wish to bring a friend or relative to accompany you to and
from the MRI department when you have your examination, although
they may not be allowed into the examination room and waiting room
space is limited.
Children
Baby changing facilities are available in the main waiting area in
X-ray Central. We are unable to offer childcare facilities – if you need
to bring your children with you please bring along somebody who
can supervise them whilst your examination is being carried out.
Further Information
You will receive a SMS text confirmation regarding your appointment.
Please follow text instructions re confirmation/appointment changes.
If you do not have a mobile your land-line will receive an automated
message to which you can respond re confirmation/appointment
changes.
If you have any questions regarding your scan or need to
change your appointment and want to speak to a member of
staff please contact the Radiology Department on: 01253 956789
NB: If you do not speak English and may require an interpreter
please arrange for a friend/ relative to contact the department
to arrange this.
Author Fiona Hopcroft
Reference Number PL/483
Date of Publication 18/09/2025
Review Date 01/09/2028
