The acronym MRI stands for ‘Magnetic Resonance Imaging‘. It is synoyomous with the small tunnel in which you have to lie, in some cases for up to an hour or so (normally 15-20 mins). Thankfully, most new modern MRI scanners are less tunnel like and some are now even upright. These later scanners are extrememly costly however and so are hard to come by presently in th UK. The images below show examples of what modern MRI scanners may look like. To get more information about the scanners click on the maufacturure below the image.
Phillips Siemans Hitachi
Fonar - (new style upright Scanner)
How Does It Work?
MRI scans differ from other common types of imagery such as X-Rays and CT scans because they use magnetic currents. The physics behind MRI technology are very complicated so for those of you who wish to jump in at the deep end or simply delve a little deeper please explore the external links at the bottom of the page.
A brief explanation is that the tunnel houses an extremely powerful electro magnetic (10,00-40000 x gravity) that when initiated, forces a small proportion of the hydrogen ions in our body to spin in line with the pull. When the magnet is then switched off, the ions spin returns to its normal orbit. When returning, the hydrogen give off a small energy signal that is picked up by the scanner and this signal is converted in to mathmatical data that eventually results in the image. Because the image is the end result of complex computer analysis, by changing the computer programming we can alter the attributes of the image (see below). This enables us to further differentiate between different structural abnormalities.
Because MRI uses harmless magnetic fields instead of X-Rays, there are no known side effects making it very safe. The only group of patients who cannot be scanned are those with metal in their bodies, but this will be screened for beforehand. A demonstration of the magnetic power on metal, and why you may not want the scan, can be seen here. Most MRI units will not scan pregnant ladies either unless there are extreme circumstances. For further information please explore the following links:
