Lumbosacral spine CT
Spinal CT; CT - lumbosacral spine; Low back pain - CT; LBP - CT
A lumbosacral spine CT is a
CT stands for computerized tomography. In this procedure, a thin X-ray beam is rotated around the area of the body to be visualized. Using very complicated mathematical processes called algorithms, the computer is able to generate a 3-D image of a section through the body. CT scans are very detailed and provide excellent information for the physician.
The spine is divided into several sections. The cervical vertebrae make up the neck. The thoracic vertebrae comprise the chest section and have ribs attached. The lumbar vertebrae are the remaining vertebrae below the last thoracic bone and the top of the sacrum. The sacral vertebrae are caged within the bones of the pelvis, and the coccyx represents the terminal vertebrae or vestigial tail.
These are the five vertebra of the lower back. The last vertebra (on the upper left of the picture) attaches to the sacrum, and the top vertebra (on the right of the picture) attaches to the thoracic section of the back. The vertebra are broader and stronger than the other bones in the spine. This allows them to absorb the added pressure applied to the lower back, but this area remains a common site of injury. The vertebra are numbered from one to five and are labeled L1, L2, L3 etc. from the higher bones to the lower.
These are twelve vertebra of the mid back. The last vertebra (on the left side of the picture) attaches to the lumbar (lower) spine, and the top vertebra (on the right) attaches to the cervical (neck) section of the back. The vertebra are broader and stronger than the cervical bones. This allows them to absorb the added pressure applied to the mid back, but they remain a common sight of injury. The vertebra are numbered from one to twelve and labeled T1, T2, T3, et cetera, from the upper most bones to the lowest.
There are five lumbar vertebrae located in the lower back. These vertebrae receive the most stress and are the weight-bearing portion of the back. The lumbar vertebrae allow movements such as flexion and extension, and some lateral flexion.
How the Test is Performed
You will be asked to lie on a narrow table that slides into the center of the CT scanner. You will need to lie on your back for this test.
Once inside the scanner, the machine's x-ray beam rotates around you.
Small detectors inside the scanner measure the amount of x-rays that make it through the part of the body being studied. A computer takes this information and uses it to create a number of images, called slices. These images can be stored, viewed on a monitor, printed on film or saved on a disk. Three-dimensional models of organs can be created by stacking the individual slices together.
You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.
In some cases, an iodine-based dye, called contrast, may be injected into your vein before images are taken. Contrast can highlight specific areas inside the body, which creates a clearer image.
In other cases, a CT of the lumbosacral spine is done after injecting contrast dye into the spinal canal during a lumbar puncture to further check for compression on the nerves. This is called a CT myelogram.
The scan usually lasts a few minutes.
How to Prepare for the Test
You should remove all jewelry or other metal objects before the test. This is because they may cause inaccurate and blurry images.
If you do need a lumbar puncture, you may be asked to stop your blood thinners or anti-inflammatory medicines (NSAIDs) several days before the procedure. Check with your health care provider ahead of time.
How the Test will Feel
The x-rays are painless. Some people may have discomfort from lying on the hard table.
Contrast may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.
Why the Test is Performed
CT rapidly creates detailed pictures of the body. A CT of the lumbosacral spine can evaluate fractures and changes in the spine, such as those due to arthritis or deformities.
What Abnormal Results Mean
CT of the lumbosacral spine may reveal the following conditions or diseases:
- Cyst
- Herniated disk
- Spinal stenosis
- Infection
- Cancer that has spread to the spine
- Osteoarthritis
- Osteomalacia (softening of the bones)
- Pinched nerve
- Tumor
- Vertebral fracture (broken spine bone)
Risks
The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, then hives, itching, nausea, breathing difficulty, or other symptoms may occur.
If you have kidney problems, diabetes or are on kidney dialysis, talk to your provider before the test about your risks of having contrast studies.
CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. The risk associated with any individual scan is small. The risk increases when many more scans are performed.
In some cases, a CT scan may still be done if the benefits greatly outweigh the risks. For example, it can be more risky not to have the exam if your provider thinks you might have cancer.
Pregnant or breastfeeding women should consult their provider about the risk of CT scans to the baby. Radiation during pregnancy can affect the baby, and the dye used with CT scans can enter breast milk.
References
Reekers JA. Angiography: principles, techniques and complications. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 78.
Van Thielen T, van den Hauwe L, Van Goethem JW, Parizel PM. Current status of imaging of the spine and anatomical features. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 47.
Version Info
Last reviewed on: 9/20/2022
Reviewed by: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
