Computed Tomography (CT or CAT) Scan of the Bones

By Sara Foster

(CT Scan of the Skeleton)

Procedure overview

Computed tomography (CT or CAT scan) is a noninvasive diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal or axial images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard X-rays.

In standard X-rays, a beam of energy is aimed at the body part being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle, and other tissue. While much information can be obtained from a standard X-ray, a lot of detail about internal organs and other structures is not available.

In computed tomography, the X-ray beam moves in a circle around the body. This allows many different views of the same organ or structure. The X-ray information is sent to a computer that interprets the X-ray data and displays it in a two-dimensional (2D) form on a monitor.

CT scans may be done with or without "contrast." Contrast refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your doctor will notify you of this prior to the procedure.

CT scans of the bones can provide more detailed information about the bone tissue and bone structure than standard X-rays of the bone, thus providing more information related to injuries and/or diseases of the bone.

Other related procedures that may be used to diagnose bone problems include X-rays of the bones, magnetic resonance imaging (MRI) of the bones, bone scan, and bone densitometry. Please see these procedures for additional information.

Reasons for the procedure

A CT scan of the bones may be performed to assess bones, soft tissues, such as cartilage, muscles, and tendons, and joints for damage, lesions, fractures, or other abnormalities, particularly when another type of examination, such as X-rays or physical examination are not conclusive.

There may be other reasons for your doctor to recommend a CT scan of the bones, joints, or soft tissues.

Risks of the procedure

You may want to ask your doctor about the amount of radiation used during the CT procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous CT scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time.

If you are pregnant or suspect that you may be pregnant, you should notify your health care provider. Radiation exposure during pregnancy may lead to birth defects. If it is necessary for you to have a CT of the bones, special precautions will be made to minimize the radiation exposure to the fetus.

If contrast dye is used, there is a risk for allergic reaction to the dye. Patients who are allergic to or sensitive to medications should notify their doctor. Studies show that 85 percent of the population will not experience an adverse reaction from iodinated contrast; however, you will need to let your doctor know if you have ever had a reaction to any contrast dye, and/or any kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast.

Patients with kidney failure or other kidney problems should notify their doctor. In some cases, the contrast dye can cause kidney failure. The effects of kidney disease and contrast agents have attracted increased attention over the last decade, as patients with kidney disease are more prone to kidney damage after contrast exposure. Also, patients taking the diabetes medication metformin (Glucophage) should alert their doctor before having IV contrast, as it may cause a rare condition called metabolic acidosis. If you take metformin, you will be asked to stop taking it 24 hours before and for 48 hours after your injection. A blood test may be required before you can start taking metformin again. 



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