CT Scan of the Body
A computed tomography (CT) scan is a special type of X-ray that can produce detailed pictures of structures inside of the body. A CT scan is also called a computerized axial tomography (CAT) scan.
A CT scanner directs a series of X-rays through the body that are analyzed by a computer to produce a detailed picture of a “slice” of an organ or area being studied. Each X-ray pulse lasts only a fraction of a second, and it takes only a few seconds for the machine to record each slice. A CT scan produces clearer pictures of internal organs (such as the liver) than regular X-rays. Information from a CT scan can be saved and stored on a computer for further study. Photographs of selected views can also be made.
Dense tissues in the body that block the most X-rays, such as bones, appear white in the pictures produced by a CT scan. The less dense tissues, such as brain tissue or muscles, appear in shades of gray. Air-filled spaces, such as in the bowel or lungs, appear black.
During a CT scan of the body, the area being studied is positioned inside a cylinder that is part of the CT scanner. The cylinder can tilt and the X-ray scanning devices within it can rotate to obtain the views needed. A CT scan is used to obtain information about the body's organs (such as the liver, pancreas, kidneys, adrenal glands, lungs, and heart), blood vessels, abdominal cavity, bones (especially of the spine), and the spinal cord. A CT scan of the brain or skull is called a CT scan of the head (see CT Scan of the Head test).
Often a special dye (contrast material) that contains iodine is injected into the blood during a CT scan. The dye makes blood vessels and certain structures or organs inside the body more visible on the CT scan pictures. The dye may be used to evaluate blood flow, detect some types of tumors, and locate areas of inflammation. Contrast material is often used to obtain images of the chest, abdomen, and pelvis. If an abdominal CT scan is done, a contrast material is usually given by mouth (orally).
How It Feels
You will feel no discomfort from the X-rays during the CT scan. However, the table you lie on may feel hard and the room may be chilly because air-conditioning is used to keep the X-ray equipment at a constant temperature. You may become uncomfortable from lying in one position for a long time.
Some people feel discomfort or anxiety (claustrophobia) when placed inside the CT scanner. If this keeps you from lying still in the scanner, you may be given a medication (sedative) to help you relax.
If contrast material is injected into your arm, you may feel warm and flushed and get a metallic taste in your mouth. In rare cases, the contrast material may cause nausea, vomiting, or a headache. If you develop these symptoms, tell the technologist or your doctor.