An MRI scan is a medical imaging procedure that uses strong magnetic fields and radio waves to produce detailed two- or three-dimensional images of the body. It does not use any x-rays so there is no radiation dose to patients. Patients do not feel anything from the magnetic fields or radio frequency pulses during the scan.
Purpose for an MRI
- MRI can be used to examine and create an image of almost any part of the body, including the:
- brain and spinal cord
- bones and joints
- heart and blood vessels
- internal organs, such as the liver, womb or prostate gland
- The results of an MRI scan can be used to help diagnose conditions, plan treatments and assess how effective previous treatment has been.
- The MRI scanning equipment consists of a large tube containing powerful magnets. An attached table slides the lying down person through the tube.
Preparation for MRI scan
- There are normally no special preparations required for an MRI scan, if any preparation is required it will be mentioned in your appointment letter. Before attending for an MRI scan you will be asked to complete a magnetic safety questionnaire. This will determine if it is safe for you to undertake the scan.
- There are some conditions which would exclude you from having an MRI scan. For example, they are not possible for people who have certain types of implants fitted, such as a pacemaker (a battery-operated device that helps control an irregular heartbeat).
What happens during an MRI scan?
- Once the magnetic safety questionnaire has been checked by a member of the MRI team you will be asked to change into a hospital gown. You will also be asked to remove all metal objects such as jewellery, watches, hairpins, glasses, hearing aids and dentures containing metal.
- You will be weighed prior to the scan, as this is required information for MRI scanning.
- On entering the MRI scanning room you will be asked to lie on the MRI scanner table and made as comfortable as possible. Specialized receiver coils (MRI antennae) will then be placed over the area we are scanning. Depending on the part of your body being scanned, you will be moved into the scanner either head first or feet first.
- You will be provided with a communications buzzer and headphones to listen to music.
- The MRI scanner is operated by a radiographer. They control the scanner using a computer, which is in a different room to keep it away from the magnetic field generated by the scanner. You will be able to talk to the radiographer through an intercom and they will be able to see you on a television monitor throughout the scan.
- During the scanning procedure we will ask you to remain very still. In some cases you may be required to hold your breath. This will all be explained to you prior to the scan.
- When scanning, the MRI scanner makes loud knocking, clicking and buzzing noises. This is the electric current in the scanner coils being turned on and off.
- It is very important that you keep as still as possible during your MRI scan, as any movements will significantly blur the images. The scan will last between 15 and 90 minutes, depending on the size of the area being scanned and how many images are taken.
- Sometimes, an injection of contrast agent is required to improve image quality. This would be discussed with you if necessary.