MRI or magnetic resonance imaging is one of the most recent medical imaging techniques. It visualises organs and soft tissues very precisely in different spacial planes. It is therefore possible to determine the exact position of lesions which would otherwise be invisible. It is performed under the supervision of a radiology doctor, and does not involve any radiation. It only uses the properties of magnetic fields.
Use of MRI
BecauseMRI allows tissue structures to be examined in great detail, it has a wide range of applications. The investigation is particularly used to examine cerebral, spinal, bone, joint, gastrointestinal, gynaecological, vascular, and heart diseases.
The procedure for an MRI
The instrument has a very powerful magnet, hence the term " magnetic". The technique involves making hydrogen nuclei vibrate as make up the body's tissues. These nuclei contain protons that act like small magnets. They emit signals by vibrating, which are taken up by a receiver and then converted into images. The patient is positioned lying down on a bed in the investigation room. The aerial is then ranged over the area which is to be examined and then the bed slides gently into the tunnel of the machine. The investigation generally takes 15 to 20 minutes.
Possible risks of MRI
Although the equipment used is noisy, MRI is not a painful investigation. Initially, all metal objects (watches, bracelets, necklaces, credit cards, etc.) must be removed from the patient. Patients must also tell the investigator if they have a heart valve or battery, prosthesis, or implants. All of these items can interfere with the investigation. Finally, note that a contrast medium may be injected. This is generally well-tolerated, but can cause allergic reactions (urticaria) which are not serious. More serious reactions are very rare and can usually be predicted from a consultation before the investigation.
Source: Société française de radiologie, website accessed on 7 January 2011.
MRI: a noisy, but painless, investigation © G3R1, Fotolia