When you visit your physician with symptoms of back pain or neck pain with or without other symptoms that may be arising from a spinal problem, he/she may often order tests to further pinpoint the source of your symptoms. These tests typically include some type of imaging (pictures) of your spine to better help guide treatment. It is important to notify your doctor if you are pregnant and/or if you have allergies to contrast agents, iodine/and or shellfish in which case you may be unable to undergo some or parts of some of these tests. You may be asked to remove any jewelry and metal accessories, and wear a gown prior to the imaging test. The following are the most common imaging tests your physician may order.
Typically, the first type of diagnostic imaging test your physician may order is a plain X-ray or radiograph. X-rays are obtained by using a small dose of radiation to penetrate bone and soft tissues of different densities to directly visualize the bony parts of the spinal column. X-rays are noninvasive and can help your physician detect aging changes in the spine and the discs (the cushions between the vertebrae), spinal alignment and curvature, spinal instability, congenital (birth) defects of the spinal column, and fractures caused by trauma, osteoporosis (loss of calcium in the bone), infections, or some tumors. Your spine specialist may order dynamic X-rays taken at different positions (ie; bending forward and backward) to assess for instability.
CT scan is a machine that uses a radiation source to obtain multiple 2-dimensional and reconstructed 3-dimensional images of body segments including the spine. Patients must lie still on a padded gurney that moves through a scanner. Multiple cross-sectional images are then obtained of the affected areas of the spine. These images provide very detailed information to your physician regarding the bony anatomy of the spine. They are especially useful in visualizing degenerative or aging changes in the spine, spinal alignment, fractures and fracture patterns, congenital/ childhood anomalies of the spine, herniated discs, and areas of narrowing in the spinal canal through which the spinal cord and spinal nerve roots pass. With the modern generation of CT scanners, entire segments of the spine can be imaged within a matter of minutes. A contrast dye may sometimes be injected through one of your veins in order to better visualize soft tissue structures and blood vessels. When performed after a myelogram (see below), CT can better identify areas where the spinal cord and spinal nerve roots are being compressed (pinched).
Myelogram is a dye study to better identify areas where the spinal cord and/or spinal nerves may be compressed. Typically, under a local anesthetic, the physician, often a radiologist, places a needle into the spinal canal in the lower back and injects a dye, which mixes with spinal fluid and runs through the spinal canal. X-rays and often a CT scan are done after the dye is injected which may show areas where the dye is blocked. These images allow your physician to visualize areas of narrowing in the spinal canal that may be causing your symptoms. A myelogram may be ordered when there is a contraindication to obtaining an MRI scan or if the deems that the images will provide additional useful information in establishing a diagnosis.
MRI has become the gold standard in establishing a diagnosis for many patients with spinal disorders. MRI uses a magnetic field to align the nuclei of hydrogen atoms in water in the body and then provides radio frequency pulses to alter this alignment. The change in the magnetic field and energy given off by these atoms is detectable by the scanner and computerized to provide detailed images inside the body. As such, it does not use ionizing radiation. In addition to identifying abnormalities of the bones of the spine, MRI is sensitive for detecting aging changes in the discs, herniated and bulging discs, areas of narrowing and compression of the spinal cord and spinal nerve roots, birth/congenital problems, spinal infections, tumors, and fractures and injuries to the soft tissues/ligaments supporting the spinal column. MRI is excellent for visualizing abnormalities of the spinal cord. Intravenous contrast is sometimes administered to better visualize certain structures or abnormalities in the spine. For the scan, patients lie still in a tubular structure and typical scan times can last 25-45 minutes. If you are claustrophobic, talk to your physician about receiving either sedation or a muscle relaxant during the MRI scan or going through an open MRI scanner. While it is noninvasive, the magnetic field associated with MRI may prevent patients with implanted metallic devices such as cardiac pacemakers, certain metal clips in the head, and stimulators to be able to undergo this test. Others with artificial joints and spinal hardware may still be able to have MRI scans. Patients must answer a questionnaire at the MRI center to deem their suitability to have an MRI test.
Discs are the cushions or joints between the vertebrae and can be a source of back or neck pain. While MRI and CT scans can provide detailed information, sometimes your specialist may order an additional test called a discogram to better identify the source of your pain. This involves placing a needle into the disc and injecting a contrast dye in the center of disc. The proceduralist then observes whether the patient experiences pain that is similar to his/her usual pain as the pressure in the affected disc is increased by injecting contrast. In addition, X-rays and often a CT scan are done after the discogram to see if the dye stays within the center of the disc or if it leaks to the outer border of disc (“leaky disc”). This may indicate a tear in the wall of the disc which can sometimes be a source of back pain.
Bone density scan, also known as dual-energy X-ray absorptiometry (DXA), is a special type of X-ray that can measure the degree of bone loss. It measures bone mineral density (BMD) which helps your physician identify whether you may have osteoporosis, osteopenia, or other diseases that increase your risk of developing fractures including those of the spine. The DXA machine uses low dose X-rays to study the bones. Differences between the bones being studied and the surrounding soft tissues are analyzed by special computer software that can calculate bone density measurements.