Imaging tests for back pain include those where doctors and other back experts may be able to view the interior structures of the back, including the intervertebral discs, vertebral spine, spinal ligaments, and back muscles. While other diagnostic tools such as a patient's medical history and the medical exam are important, imaging tests give doctors a definitive look at the internal structures of the back, and the general state of a person's spine. The most common imaging tests that are used to determine the cause of back pain are X-Rays, CT Scans, and MRIs.
X-Rays are the cheapest medical imaging tests, and may be a good first step for doctors to get a view of the general state of a person's spine, and whether disorders related to the spinal bones and discs exist. X-Rays are black and white images, and use electromagnetic radiation to produce images of contrasting densities on pictures. These pictures may be viewed on film or computer. In a nutshell, here's how they work.
During an X-ray exposure, a huge amount of energy is fired from cathode to an anode. At the anode, this energy is converted to X-ray photons and is propelled towards your body. Some of these photons are absorbed from your body, and some are able to pass through it to hit the image receptor. The denser objects in your body, such as the bones and teeth, absorb many of these X-ray photons. The less dense structures, such as the joints and other connective tissues allow more X-Ray photons to pass through your body. An image will be produced based on the contrasting densities of information that are collected on the image receptor.
An X-Ray is used at detecting structural anomalies related to the vertebral bones. Anomalies related to the spinal bones that may be confirmed by reading X-ray films include fractures, scoliosis, bone density loss, and instability of the spine. Spondylolisthesis is one type of spinal instability in which X-ray images indicate that one or more vertebral bones has slipped forwards or backwards from its correct position in the spine. X-rays may also be used to confirm the existence of tumors.
CT Scans: CT Scans, also known as computed tomography, also use electromagnetic radiation. These types of imaging tests provide more 3D images than X-rays by taking cross section images of the body. CT Scans, also known as computerized tomography, are better than X-Rays for evaluating spinal conditions such as spinal stenosis and disc herniation. These scans take X-Ray images that build a three dimensional view of the spine structures by combining the cross sections that are photographed and stored on the computer. CTs are good for showing the vertebral bones in great detail, but are not sensitive enough to show the nerve roots in great detail. To get a more defined look at the nerve roots, and MRI may be ordered.
MRI (Magnetic Resonance Imaging): MRIs give the doctors the ability to diagnose problems with the spinal anatomy that may not present on X-Rays and CT Scans. MRI's work by using surrounding your body with a magnet that align the elements in your body to react a certain way. The atoms in your body, such as hydrogen, spin a certain way in response to the magnetic field created by the MRI tube. Different structures in your body react to the MRI magnet differently based on how much hydrogen they contain.
MRI tests may be good as confirming spinal anomalies such as tumors, infection, nerve root compression, and compression of the nerves of the spinal cord.
EMG (Electromyography): In many cases, patients experience muscle pain and muscle spasms because of compression of the spinal nerves that supply those muscles. In an EMG test, doctors insert needles into certain muscles to determine whether the firing of those muscles is normal or due to spontaneous electrical activity. These types of tests will be ordered in cases where muscle tension exists, and this muscle tension is thought to be related to pinched nerves. Typically, the electrical activity in our muscles intensifies when the muscles contract. Our back muscles contract more intensely when we are using them for activities such as lifting heavy objects and arching our backs. These muscles contract or relax based on the electrical impulses that come from the nerves, which originate at the nerve roots. In cases of chronic compression of the nerve or nerve root, these signals may not be conveyed to the muscles. The result may be the loss of motion of that muscle, muscle tightness, or muscular de-conditioning. EMG tests are used to recognize when the muscles begin to contract spontaneously as a result of nerve root compression (also known as a pinched nerve).
EMG tests may be used to confirm the diagnosis of nerve root compression (radiculopathy) and nerve degeneration (neuropathy).
Unlike other types of imaging tests, this diagnostic procedure may be somewhat painful, because it involves the placement of needles directly into the muscles. Electromyography is not as common as other tests because of the potential discomfort involved and because they are not considered to be highly reliable, in terms of determining which nerves are compressed.