Computed tomography of the chest is a noninvasive imaging method that combines x-rays with computer technology. X-ray beams from many angles are used to create a series of detailed cross sectional images.
Computed tomography can provide detailed views of several types of tissue including lung, bone, soft tissue and blood vessels. For this reason, this technique is an excellent method for determining the size and location of growths that are suspected to be cancer. It is also used to guide radiation therapy, biopsies, and other minimally invasive procedures. Conditions of the lungs and chest wall frequently diagnosed with chest CT include: tumors and other abnormal growths, including lung cancerbroken ribsabscesses, such as those caused by tuberculosisenlarged lymph nodesfluid around the lungs, or pleural effusionabnormalities of the blood vessels supplying the lungsconditions of the esophagus and stomach
Before the test the healthcare professional will ask the person if he or she: has any drug allergies, or history of allergic reaction to medicationsis allergic to shellfish, or foods with added iodine such as table salthas experienced claustrophobia, or anxiety in enclosed spaces. If this is a problem, mild sedating medication may be given.
A woman will be asked if there is a possibility she might be pregnant. If the answer is "yes", the test cannot be done unless a pregnancy test is negative. The person having the test will lie on a flat table. The CT technologist may use pillows or other devices to help support the individual's body in the proper position.
As the test begins, the table will move slowly into a donut-shaped machine. This device delivers x-ray beams through the person's chest cavity from many angles. Often, special substances called "contrast agents" are used to enhance internal structures and improve image quality on the final image. For a chest CT, contrast agents are most commonly injected into a vein or swallowed.
Before using some contrast agents, the normal functioning of the kidneys may be checked with blood tests to make sure the kidneys are working well enough to get rid of the contrast agent from the body. If contrast is administered, the patient may experience mild nausea, flushing, itching or a metallic taste in the mouth. Most of these sensations disappear within a few minutes.
A conventional chest CT test takes approximately 30 to 45 minutes. More advanced CT devices, known as helical or spiral CT machines, reduce the imaging time dramatically. To prevent distortion of the final images, the person must lie very still for the duration of the test.
After the test, the person will be asked to wait until the images are examined to see if more images are needed. The person will be observed for any delayed allergic reactions to the medication used as the contrast agent. Also, the individual will be encouraged to drink extra fluids to help flush the contrast material from the body.
The person having a CT will need to refrain from eating or drinking at least 4 hours prior to the test. The CT technologist will explain the procedure to the individual. People who are prone to claustrophobia may be administered a calming drug before the exam.
A doctor specially trained in analyzing CT images, called a radiologist, will examine the results of the test. The radiologist will forward a report of the findings to the individual's healthcare professional.
Some of the conditions a chest CT can reveal include: tumors of the lungs, chest wall, bone and soft-tissue, such as lung cancerlung abscesslung infections such as pneumonia and tuberculosischronic lung conditions such as emphysemafluid or inflammation of the membranes around the heart, known as pericardial effusionfluid or inflammation of the membranes around the lungs, known as pleural effusionrib or spine fracturesstomach conditions, such as hiatal hernia or conditions of the esophagusenlarged lymph nodesconditions of the aorta such as calcification, dilation, or tears
Pagana, Kathleen D. and Timothy J. Pagana, Mosby's Manual of Diagnstic and Laboratory Tests, St. Louis, 1998.
"Computed Tomography (CT) - Body," Radiological Society of North America (RSNA), 2000.