MRI-Magnetic Resonance Imaging
Figure 1: Narrow
degenerated disc (MRI)
An MRI scan may be ordered as an advanced imaging study to better visualize specific regions of the spine. MRI scans are best for evaluating the soft tissues of the spine, including the intervertebral discs and spinal cord and nerves. [Figure 1 ] MRI visualized bone least well of all tissues, and the scan is often done along with or following x-rays or a CT scan. MRI scans are often performed to diagnose and evaluate degenerative disc disease, herniated discs, and spinal stenosis. [Figure 2 ]. They are also used to diagnose infection and tumors in the spine and to follow the progress of patients with recurrent symptoms after spine surgery.
MRI is a safe noninvasive imaging technology that uses radiofrequency waves and the natural magnetic properties of tissues within an enhanced magnetic field (created by the MRI scanner). This information is then used with computers to reconstruct cross-sectional images which are not possible to do with X-rays. Patients with pacemakers cannot have MRI scans. If you have a pacemaker, your doctor can choose other diagnostic tests (CT scan or myelogram). Other contraindications to MRI imaging are the presence of metallic clips in the brain or an implantable neurostimulator for chronic pain control. In general, most patients with joint replacement implants and previous spinal metal implants can safely undergo MRI testing of other areas of the body.
Figure 2: Herniated disc with
fragment pushing against
the spinal nerves (MRI).
Closed MRI provides superior images compared to open MRI and is the type of MRI scan recommended by the HJD Spine Center. The tube of the closed scanner is smaller, allowing the magnet of the scanner to be closer. This creates a stronger magnetic field, making better images. Most patients are able to tolerate a closed MRI without difficulty. Patients lie on their back in a large partially enclosed tube for usually no more than 45 min. Newer .short-boreê closed magnets allow for a patientês head to be positioned outside of the scanner while a low-back MRI is being performed.
In some circumstances, the physician may request a contrast-enhanced MRI where a nontoxic dye is injected into an arm vein through a small needle. An MRI scan is partially done before the dye injection, and then additional sequences are done after the dye injection. Among other things, the contrast dye helps to differentiate between scar from previous surgery and disc material. Use of contrast dye is most common in evaluating patients with continued or recurrent pain who have had previous spinal surgery.