This overview is a sample of the type of information available to you at Griffin Hospital's Community Health Resource Center. It is not intended to replace your physician's instructions in the management of your health problems, but to better inform you about a particular illness and alert you to the availability of other materials. If you have a question about any piece of information presented in theses fact sheets, please call your physician, or stop by the Community Health Resource Center at your convenience.

CT SCAN OF THE CHEST

(Computerized Axial Tomography, CAT Scan, Lung Scan)

Although the CT scan is a relatively new technique, it provides such valuable information that it is frequently used in diagnosing a variety of disorders, including tumors, cysts, lesions, abscesses, and broken blood vessels.

CT scans are performed in the radiology department by nurses or technicians specially trained to operate CT scanning equipment. The scanning machine is very large and looks like a giant, six-foot doughnut. The hole is in the doughnut is designed to be big enough for a person lying on the x-ray table to be moved back and forth through it.

An x-ray tube or "camera" is mounted inside a ring surrounding the doughnut hole. As the x-ray tube rotates around your body, a computer in the next room measures from each angle the amount of energy absorbed by your body tissue. By analyzing this information, the computer converts it into a picture of the internal organs of your body, showing very subtle differences in the densities. (The differences in densities appear as different shades of gray similar to a black and white photograph). The picture, which appears first on the computer's screen, is different from a regular x-ray because it shows a cross-section of your body (looking down through your body)

from the front, back, or side.

After the computer has analyzed one picture, the table you are lying on will be slightly moved so a picture of a different cross-section can be made. A CT scan usually involves from 10 to 30 different pictures, depending on how large an area is being examined.

For a CT scan of the chest, you will be asked to lie on the table with your arms extended over your head. This is an awkward position, but it is important that you lie very still throughout the entire procedure, which may take up to an hour. Try to make yourself as comfortable as possible before the test begins. Ask for a blanket if you are cold, or ask to have your knees propped up on pillows.

After you have been comfortably positioned on the table, the technician will go into an adjacent room where the computer that operates the scanner is located. He or she will be able to observe you through a window and give you instructions as needed.

When the procedure begins, your body will be moved into the ring of the scanner either head first or feet first. The table will be positioned so that your chest remains inside the ring. You will hear the click and whiz of gears and motors as the x-ray tube rotates around you, but there is no pain involved. Some patients, however, complain of feeling claustrophobic when their bodies are inside the scanner, but they sometimes find that by closing their eyes they can relax. Although each scan takes only a few seconds, there may be a delay of several minutes between each picture while the technician waits for the computer to compile the picture.

After some of the scans are completed, you may be given contrast dye to help highlight certain internal structures. For a CT scan of the chest, the dye is usually given intravenously (IV). The dye will either be slowly dripped in or quickly pushed in with a syringe. As the dye enters your bloodstream, especially if it is given rapidly, you may feel a warm sensation in your arm or throughout your body. Other side effects from the dye include a strange metallic taste in your mouth and sometimes nausea. Some doctors recommend that you avoid eating for several hours prior to the exam to reduce the chances of vomiting.

If you are allergic to seafood or iodine, you may also be allergic to the contrast dye. Inform your nurse, doctor, or technician of your allergies before the dye is given. If you experience itching, hives, or difficulty breathing after the dye is given, tell the technician immediately since these could be signs of an allergic reaction. You could then be given medication to minimize these effects. For most patients, the side effects are very mild and last for only a few minutes. Many patients say that the greatest discomfort is the urge to urinate as the dye is filtered out of the bloodstream by the kidneys. Emptying your bladder before the scanning begins can help to avoid this problem.

After the scan is over, you may be asked to wait until a radiologist has seen the pictures in case more scans are needed. Then you can return to your room and resume your normal activities and diet. You may be requested to drink extra fluids to help flush the dye out of your blood stream.

Later, a radiologist will examine the pictures from the scan and send a written report to your doctor. This information should be available within a few days.

Please note that this information is intended to give you a general overview of the topic. It is not intended to replace advice or instruction of a health professional. We recommend that you consult your physician, nurse, or qualified health professional regarding the information in this publication. © 1994 Planetree, Inc. Reproduction of this material in any form is limited to license agreement.

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