MRI

Magnetic Resonance Imaging (MRI) is different to CT and x-rays as it uses a very powerful magnetic field instead of radiation to get incredibly detailed pictures of the inside of the body. Because of the powerful magnetic field all patients, staff and visitors who are going into the scan room must complete a safety questionnaire and remove all metal such as watches, jewelry, phones, money, wallets, etc. All the additional equipment that is needed for patients such as wheelchairs, trolleys, drip stands, anaesthetics and monitoring equipment has to be specially purchased and check to ensure that it is compatible with the strong magnetic field.

Any area of the body can be scanned from the head to the toes, looking at blood vessels, nerves, muscles and other soft tissue, however MRI scans are not quick and an average set of pictures will take 30 to 45 minutes per patient.

MRI provides cross sectional imaging without the use of ionising radiation and should be considered in preference to CT when both investigations could yield similar information.

As with all radiological requests, any MRI referral should be provided with sufficient clinical information to allow justification. Examinations that fall outside established guidelines can be discussed with a radiologist.

Points for consideration:

• Contraindications to the use of MRI include metallic foreign bodies in the orbits, aneurysm clips, pacemakers and cochlear implants. Furthermore, MRI will give reduced image quality close to prostheses. Possible contraindications should be discussed with the imaging department well in advance of the proposed investigation.
• The safety of MRI during the first trimester of pregnancy is uncertain. However, it may well be safer than some of the alternative options. All imaging of pregnant women should be discussed with the radiology department.

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