Computed Tomography Scan of the Bones, Skeletal CT Scan
In bone CT scan, a body scanner delivers x-rays to selected bones or joints—such as the shoulder, spine, hip, or pelvis—at many different angles. A computer compiles this information to construct highly detailed, cross-sectional images, which are then displayed on a TV monitor and recorded on x-ray film.
In some cases, a contrast dye may be injected to enhance detail of the bones and the soft tissue inside and around the bones on the images.
A variation of bone CT scan, called myelography, involves injection of a contrast dye directly into the spinal canal to provide fine detail of the spine, spinal cord, and surrounding tissues.
Purpose of the Bone CT Scan
- To identify abnormalities in the upper and lower spine, such as herniated discs and spinal stenosis (a narrowing of the spinal canal), that may be causing back pain and/or referred pain to the lower extremities
- To detect and assess the extent of primary or metastatic bone tumors, and tumors in the soft tissue surrounding bones
- To diagnose joint abnormalities, such as fractures through the joint surface and certain tumors, that are difficult to detect with other methods
- To determine the location of an abscess
- To evaluate skeletal changes in osteoporosis and other metabolic bone diseases
- To diagnose bone loss (osteoporosis), which is common in women after menopause and also may occur in men
- To evaluate fracture risk
- To detect unusually active formation of bone
Who Performs Bone CT Scan
Special Concerns about Bone CT Scan
- Pregnant women should not undergo this test because exposure to ionizing radiation may harm the fetus.
- People with allergies to iodine or shellfish may experience an allergic reaction to iodine-based contrast dyes.
- Painkillers may be administered to people with significant bone or joint pain if remaining still during the exam is likely to cause discomfort.
- People who experience claustrophobia may find it difficult to undergo a CT scan, which takes place in a narrow, tunnel-like structure.
- This test may not be possible for severely overweight individuals (over 300 lbs).
Before the Bone CT Scan
- Avoid taking calcium supplements for at least 24 hours before the test
- Inform your doctor if you have an allergy to iodine or shellfish. You may be given a combined antihistamine-steroid preparation to reduce the risk of an allergic reaction to the contrast dye.
- Tell your doctor if you suffer from claustrophobia. He or she may prescribe a sedative to help you tolerate the procedure.
- Tell your doctor if you had a recent barium examination, computed tomography (CT) scan with contrast material or radioisotope scan. A period of 10 to 14 days is necessary between these procedures and a bone scan.
- Tell your doctor if you are pregnant or may be pregnant.
- If a contrast dye is to be used or if sedation is anticipated, you will be instructed to fast for 4 hours before the test.
- You will be asked to remove your clothes, jewelry, and any metal objects and put on a hospital gown.
What You Experience during Bone CT Scan
- You will lie on your back on a narrow table that is then advanced into the CT scanner.
- The scanner, which encircles you, rotates around you taking pictures at different intervals and from various angles. You will feel the table move during the test.
- You must remain as still as possible because any movement can distort the images on the scan.
- The examiner may advise you on how to control your breathing at several points during the procedure.
- A contrast dye may be administered through an intravenous (IV) needle or catheter inserted in a vein in your arm. You may feel a brief warm, flushing sensation after the injection; rarely, some people experience nausea and possibly vomiting.
- The test typically takes 30 to 60 minutes.
Risks and Complications of Bone CT Scan
- CT scanning involves exposure to low levels of radiation.
- Some people may experience an allergic reaction to the iodine-based contrast dye, which can cause symptoms such as nausea, sneezing, vomiting, hives, and occasionally a life-threatening response called anaphylactic shock. Emergency medications and equipment are kept readily available.
After the Bone CT Scan
- You are free to resume your normal diet and activities.
- If a contrast dye was used, you are encouraged to drink clear fluids to avoid dehydration and help flush the material out of your system.
- Blood may collect and clot under the skin (hematoma) at the dye injection site; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.
- Delayed allergic reactions to the contrast dye, such as hives, rash, or itching, may appear 2 to 6 hours after the procedure. If this occurs, your doctor will prescribe antihistamines or steroids to ease your discomfort.
Results of Bone CT Scan
- A physician will examine the recorded images for evidence of abnormalities in the bones or joints being examined.
- If a definitive diagnosis can be made, appropriate treatment will be initiated, depending on the specific problem.
- In some cases, additional tests may be needed to establish a diagnosis and determine the extent of the problem. For example, magnetic resonance imaging may provide better detail of the soft tissues near the spine.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media