What is CT Scanning of the Chest?

Computed tomography, more commonly known as a CT or CAT scan, is a diagnostic medical imaging test. Like traditional x-rays, it produces multiple images or pictures of the inside of the body.

A CT scan generates images that can be reformatted in multiple planes. It can even generate three-dimensional images. Your doctor can review these images on a computer monitor, print them on film or via a 3D printer, or transfer them to a CD or DVD.

CT images of internal organs, bones, soft tissue, and blood vessels provide greater detail than traditional x-rays. This is especially true for soft tissues and blood vessels.

Doctors can use a variety of techniques to lower the amount of radiation needed to perform a chest CT scan. These techniques include adjusting the radiation dose based on patient size and new software technology. A low-dose chest CT produces images of enough quality to detect many lung diseases and abnormalities using much less radiation than a conventional chest CT scan. In some cases, doctors may lower the dose by 65 percent or more. Doctors routinely use low-dose chest CT to evaluate acquired and congenital lung abnormalities. These include pneumonia, interstitial lung disease, and tumors. There is ongoing research to lower radiation doses even further. Your radiologist will decide the proper settings for your scan depending on your medical issue and what information the CT scan needs to obtain. If your child is to have a CT scan, the doctor will use low-dose pediatric settings.

What are some common uses of the procedure?

Doctors use chest CT to:

• examine abnormalities found on chest x-rays.
• help diagnose the causes of signs or symptoms of chest disease, 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 heart, blood vessels, lungs, ribs and spine.

Chest CT can demonstrate various lung disorders, such as:

• benign and malignant tumors
• pneumonia
• tuberculosis
• bronchiectasis, cystic fibrosis
• inflammation or other diseases of the pleura (the covering of the lungs)
• interstitial and chronic lung disease
• congenital abnormalities

The Centers for Medicare and Medicaid Services approves of CT scanning for lung cancer screening of smokers and ex-smokers who meet certain criteria. See the Lung Cancer Screening page for more information.

Your doctor may perform a CT angiogram (CTA) to evaluate the blood vessels (arteries and veins) in the chest. The technologist  rapidly injects an iodine contrast material into a vein while obtaining CT images. See the CT Angiography (CTA) page for more information.

Who interprets the results and how do I get them?

A radiologist, a doctor specially trained to supervise and interpret radiology exams, will analyze the images. The radiologist will send an official report to the doctor who ordered the exam.

You may need a follow-up exam. If so, your doctor will explain why. Sometimes a follow-up exam further evaluates a potential issue with more views or a special imaging technique. It may also see if there has been any change in an issue over time. Follow-up exams are often the best way to see if treatment is working or if a problem needs attention.

What are the benefits vs. risks?

Benefits

• CT is fast, which is important for patients who have trouble holding their breath.
• CT is widely available.
• CT scanning is painless, noninvasive, and accurate.
• A major advantage of CT is its ability to image bone, soft tissue, and blood vessels all at the same time.
• Unlike conventional x-rays, CT scanning provides very detailed images of many types of tissue as well as the lungs, bones, and blood vessels.
• CT exams are fast and simple. In emergency cases, they can reveal internal injuries and bleeding quickly enough to help save lives.
• CT has been shown to be a cost-effective imaging tool for a wide range of clinical problems.
• CT is less sensitive to patient movement than MRI.
• Unlike MRI, an implanted medical device of any kind will not prevent you from having a CT scan.
• CT imaging provides real-time imaging, making it a good tool for guiding needle biopsies and needle aspirations. This is particularly true of procedures involving the lungs, abdomen, pelvis, and bones.
• A diagnosis via CT scan may eliminate the need for exploratory surgery and surgical biopsy.
• No radiation remains in a patient's body after a CT exam.
• The x-rays used for CT scanning should have no immediate side effects.
• Low-dose CT scans of the chest use a lower dose of radiation than conventional chest CT.

Risks

• There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk involved with CT scanning.
• The radiation dose for this procedure varies. See the Radiation Dose page for more information.
• Women should always tell their doctor and x-ray or CT technologist if there is any chance they are pregnant. See the Radiation Safety page for more information about pregnancy and x-rays.
• Doctors do not generally recommend CT scanning for pregnant women unless medically necessary because of potential risk to the unborn baby.
• The risk of serious allergic reaction to contrast materials that contain iodine is extremely rare. Radiology departments are well-equipped to deal with such reactions.
• In some patients with reduced kidney function, CT contrast material may worsen kidney function.
• There is a small chance of contrast leakage outside the vein at the site of an IV insertion site (“extravasation”). However, the technologist monitors for IV problems and the amount of leakage is usually small and easily treated.

What are the limitations of CT Scanning of the Chest?

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

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

Even though the CT exam is very fast, motion from breathing or body movement during the exam may result in blurring of the images.