MRI
MRI Patient Information
MRI Patient Safety Questionnaire
What is MRI?
MRI is known as Magnetic Resonance Imaging. It is an imaging technique which uses a very strong magnet and radio frequency energy, to produce images in any plane through the body. MRI does not use x-rays.
The images produced can be acquired in different ways to demonstrate certain anatomy or pathology. MRI images show the soft tissues of the body (muscles, nerves, brain, discs, ligaments etc).
During the scan you will be lying inside the bore of a large cylindrical magnet. It is important that you are still during the scan because even slight movement can spoil the images and reduce their usefulness. Every effort will be made to ensure that you are comfortable during your scan.
Music is provided in headphones from an FM radio, or from your own CD which you can bring in. TV can also be viewed during your scan by using specially constructed mirrored glasses.
How long does the MRI take?
Most MR scans take between 20 and 40 minutes. The radiographers will communicate to you during the scan through an intercom system.
Safety Issues
Due to the strong magnetic fields used, patients and accompanying staff need to be aware of several important safety issues.
1. Absolute Contraindications
Patients with implanted cardiac pacemakers, infusion pumps, brain aneurismal clips, cochlear implants or metal foreign body in the eye will not be admitted to the scan room due to risk of injury to the patient.
2. External metal objects:
No loose metal objects can be taken inside the scan room. This includes things such as jewellery, keys, paper clips and scissors. They can be attracted to the magnetic field and become dangerous missiles.
No electronic devices can be taken inside the scan room. This includes things such as infusion pumps, mobile phones, pagers, watches and credit cards. The magnetic field may irreversibly damage these things.
3. Internal metal objects:
Patients with implanted electronic devices such as pacemakers, infusion pumps and cochlear implants will not be admitted into the MRI scan room because there is a danger of injury to the patient if the device malfunctions due to the magnetic field.
Patients with intracerebral aneurysm clips will not be admitted to the scan room because the magnetic field may move the clips. The brain does not produce scar tissue so any movement of these clips could cause the aneurysm to rupture.
Patients with metal fragments within the eyeball will not be admitted to the scan room because movement of the metal by the magnetic field may injure the patientÃs eye.
Other surgically implanted metal devices, such as those used in orthopaedic, cardiac or abdominal surgery are mostly MRI compatible, but still need to be checked with the MRI radiographer.
Preparation for MRI
All patients (or a relative, if the patient is unable to) must fill out the MRI Safety questionnaire.
All patients, regardless of type of examination, are changed into a gown, with all external metal objects removed.
There is no other preparation required. Food, drink and medication can be continued.
The only exception to this is the MRCP (for biliary system).
The preparation for MRCP is nil orally for 8 hours prior to the scan.
Claustrophobia
If you have experienced claustrophobia, or have trouble in enclosed spaces talk about it with the MRI staff before your appointment date.