Computed Tomography (CT or CAT) Scan of the Chest

By Emma Hitt

(Chest CT Scan, Thoracic CT Scan, CT of the Thorax)

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 both horizontal and vertical cross-sectional 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 physician will notify you of this prior to the procedure.

CT scans of the chest can provide more detailed information about organs and structures inside the chest than standard x-rays of the chest, thus providing more information related to injuries and/or diseases of the chest (thoracic) organs.

CT scans of the chest may also be used to visualize placement of needles during biopsies of thoracic organs or tumors, or during aspiration (withdrawal) of fluid from the chest. CT scans of the chest are useful in monitoring tumors and other conditions of the chest before and after treatment.

Other related procedures that may be used to diagnose problems of the lungs and respiratory tract include bronchoscopy, bronchography, chest fluoroscopy, chest x-ray, chest ultrasound, lung biopsy, lung scan, mediastinoscopy, oximetry, peak flow measurement, positron emission tomography (PET) scan, pleural biopsy, pulmonary angiogram, pulmonary function tests, sinus x-ray, and thoracentesis.

Reasons for the Procedure

The chest contains organs of the respiratory and cardiovascular systems, as well as the esophagus (hollow tube of muscle extending from below the tongue to the stomach). A CT scan of the chest may be performed to assess the chest and its organs for tumors and other lesions, injuries, intra-thoracic bleeding, infections, unexplained chest pain, obstructions, or other conditions, particularly when another type of examination, such as x-rays or physical examination, is not conclusive.

A CT scan of the chest may also be used to evaluate the effects of treatment of thoracic tumors. Another use of chest CT is to provide guidance for biopsies and/or aspiration of tissue from the chest.

There may be other reasons for your physician to recommend a CT scan of the chest.

Risks of the Procedure

You may want to ask your physician 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 physician. 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 physician. Radiation exposure during pregnancy may lead to birth defects.

If contrast dye is used, there is a risk f or allergic reaction to the dye. Studies show that eighty-five percent of the population will not experience an adverse reaction from iodinated contrast; however, you will need to let your physician 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.



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