MRI is a body imaging system employing a magnet which surrounds the patient. A magnetic field causes small harmless movement of atoms in the head and a low energy radio wave is then passed through the same area. The minute change this imparts to the atoms in the magnetic field causes signals to be emitted which are picked up and analysed by modern computer technology. An image of the brain is produced in clear detail.
An MRI scan takes longer than a CT scan but again involves lying still on a table that moves you into the scanner. Unlike CT, the space is more enclosed and patients with severe claustrophobia may find it intolerable or require sedation before the scan. The machine makes a banging sound during scanning and you may be given headphones or ear plugs. You can talk to or summon the operator at any time. Again you may be given an injection of dye during the scan.
As the MRI does not involve X-rays there is not any known risk to a foetus but it is advisable for female patients to report any pregnancy to the staff anyway. As the scan relies on a strong magnetic field you will be asked to remove any magnetic objects from your person and you should report to the staff any metal implants (pacemakers, stimulators, internal ear implants, aneurysm clips, metallic heart valves, metallic splinters, etc.).