CT scanning—sometimes called CAT scanning—is a noninvasive medical test that helps physicians diagnose and treat medical conditions.

CT scanning combines special x-ray equipment with sophisticated computers to produce multiple images or pictures of the inside of the body. These cross-sectional images of the area being studied can then be examined on a computer monitor, printed or transferred to a CD.

CT scans of internal organs, bones, soft tissue and blood vessels provide greater clarity and reveal more details than regular x-ray exams.

Using a variety of techniques, including adjusting the radiation dose based on patient size and new software technology, the amount of radiation needed to perform a chest CT scan can be significantly reduced. A low-dose chest CT produces images of sufficient image quality to detect many lung diseases and abnormalities using up to 65 percent less ionizing radiation than a conventional chest CT scan. This is especially true for detecting and following lung cancer. Other diseases, such as the detection of pulmonary embolism and interstitial lung disease may not be appropriate for low-dose chest CT. Your radiologist will decide the proper settings to be used for your scan depending on your medical problems and what information is needed from the CT scan. If your child is to have a CT scan, the proper low-dose pediatric settings should be used.

CT of the chest is used to:

• further examine abnormalities found on conventional chest x-rays.
• help diagnose the cause of clinical signs or symptoms of disease of the chest, such as cough, shortness of breath, chest pain, or fever.
• detect and evaluate the extent of tumors that arise in the chest, or tumors that have spread there from other parts of the body.
• assess whether tumors are responding to treatment.
• help plan radiation therapy.
• evaluate injury to the chest, including the blood vessels, lungs, ribs and spine.
• further evaluate abnormalities of the chest found on fetal ultrasound examinations.

Chest CT can demonstrate various lung disorders, such as:

• lung cancer.
• old or new pneumonia.
• tuberculosis.
• emphysema.
• bronchiectasis.
• inflammation or other diseases of the pleura, which covers the lungs.
• diffuse interstitial lung disease.
• congenital abnormalities.

A CT angiogram (CTA) may be performed to evaluate the blood vessels (arteries and veins) in the chest. This involves the rapid injection of an iodine-containing fluid (contrast material) into a vein while obtaining numerous, thinner CT images.

Because CT scans are able to detect even very small nodules in the lung, chest CT is especially effective for diagnosing lung cancer at its earliest, most curable stage. As a result, two major clinical trials are underway to determine if CT scanning is helpful at reducing deaths from the disease and to study the benefits associated with the early detection of lung cancer by CT screening.

Depending on the results of this research, low-dose chest CT may become a screening tool for detecting lung cancer in current and former smokers as well as other individuals who have a high risk of developing lung cancer.

A person who is very large may not fit into the opening of a conventional CT scanner or may be over the weight limit for the moving table which is usually about 450 pounds.

Magnetic resonance imaging (MRI) may be better than CT for showing some types of soft-tissue abnormalities.