An MRI scan is particularly useful as an aid in the assessment of certain back conditions by providing detail of the spinal disc (such as for degenerative disc disease, isthmic spondylolisthesis) and nerve roots (such as for lumbar disc herniation, lumbar spinal stenosis). MRI scans are also useful to rule out tumors or spinal infections.
How an MRI Scan Works
An MRI images the spine by using a magnet that goes around the body to excite hydrogen atoms. After the atoms return to their normal level of excitation, they emit energy that is picked up on an MRI scanner. Since humans are composed primarily of water (which is two parts hydrogen), MRI scans provide highly refined detail of the spine's anatomy (see Figure 1).
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Unlike an x-ray beam, there is no radiation with the magnet so the MRI scans may be done for pregnant women. However, patients with a pacemaker implanted in their heart should not have an MRI scan because the magnetic field will cause the pacemaker to malfunction. Also, anyone who works around metal should first have an x-ray of their eye sockets to ensure that they do no have any metal filings in their eyes, which the magnetic field may cause to migrate and damage the eye during the MRI scan.
New Developments in MRI Scan Equipment
Because most MRI scanners are fairly tight, certain patients with back pain, neck pain and other symptoms may feel uncomfortable, or may not tolerate, lying in a tight tunnel for 45 to 60 minutes while the scan is being performed. To address this issue, newer generation MRI scanners are designed with more open space, although a more open tube does sacrifice the excellent detail provided by the tight tubes.