• About |
• What To Expect |
• Patient Preparation |
• Common Uses for the Test |
• Risks and Benefits

About

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. CT scans of internal organs, bone, soft tissue and blood vessels provide greater clarity and reveal more details than regular x-ray exams. CT has revolutionized medicine because it allows doctors to see diseases that, in the past, could often only be found at surgery or at autopsy. CT is noninvasive, safe, and well-tolerated. It provides a highly detailed look at many different parts of the body. People often have CT scans to further look at an abnormality seen on another test such as an x-ray or an ultrasound. They may also have a CT to check for specific symptoms such as pain or dizziness. People with cancer may have a CT to look for the spread of disease. CT is used to when patient's have headaches, or suspected stroke.

What To Expect

Most CT scans are conducted as an outpatient procedure. You have the test and then go home. The CT scanner looks like a large donut with a narrow table in the middle. Unlike MRI, in which you would be placed inside the tunnel of the scanner, when undergoing a CT, you rarely experience claustrophobia because of the openness of the doughnut shape of the scanner. Typically you lie on your back on the table, which moves through the center of the machine. You move through the scanner either head first or feet first, depending on the part of the body being scanned. You must remain motionless for the length of the study, which is typically just a few minutes. The entire procedure, which includes set-up, the scan itself, checking the pictures, and removing the IV if needed, takes 15-45 minutes depending on what part of the body is being scanned.

• For some studies, you will be asked to hold your breath for up to 20 seconds.
• What clothing you wear depends on the nature of the study. For a CT of the chest, abdomen, or pelvis, for example, usually you will change into a gown. For a head CT, you can wear normal street clothes.
• Sedation is rarely necessary. The machine is quiet, so all you hear during the test is a quiet whirr.
• The technologist is in the next room and can observe you through a large window.

How long will it take?
The entire procedure, which includes set-up, the scan itself, checking the pictures, and removing the IV if needed, takes 15-45 minutes depending on what part of the body is being scanned.

Patient Preparation

Unless you were told at the time of scheduling your CT there is no preparation is needed.

You should wear comfortable, loose-fitting clothing to your exam. You may be given a gown to wear during the procedure. Metal objects including jewelry, eyeglasses, dentures and hairpins may affect the CT images and should be left at home or removed prior to your exam. You may also be asked to remove hearing aids and removable dental work.

You may be asked not to eat or drink anything for several hours beforehand, especially if a contrast material will be used in your exam. You should inform your physician of any medications you are taking and if you have any allergies. If you have a known allergy to contrast material, or "dye," your doctor may prescribe medications to reduce the risk of an allergic reaction.

If you are to have a contrast injection, you should not have anything to eat or drink for a few hours before your CT scan because the injection may cause stomach upset. To receive the contrast injection, an IV is inserted into your arm just prior to the scan. The contrast then enters your body through the IV.

Prior to most CT scans of the abdomen and pelvis, it is important to drink an oral contrast agent that contains dilute barium. This contrast agent helps the radiologist identify the gastrointestinal tract (stomach, small and large bowel), detect abnormalities of these organs, and to separate these structures from other structures within the abdomen. You will be asked to drink slightly less than a quart spread out over 1.5-2 hours.

Common Uses for the Test

CT imaging is:

• one of the best and fastest tools for studying the chest, abdomen and pelvis because it provides detailed, cross-sectional views of all types of tissue.
• often the preferred method for diagnosing many different cancers, including lung, liver and pancreatic cancer, since the image allows a physician to confirm the presence of a tumor and measure its size, precise location and the extent of the tumor's involvement with other nearby tissue.
• an examination that plays a significant role in the detection, diagnosis and treatment of vascular diseases that can lead to stroke, kidney failure or even death. CT is commonly used to assess for pulmonary embolism (a blood clot in the lung vessels) as well as for abdominal aortic aneurysms (AAA).
• invaluable in diagnosing and treating spinal problems and injuries to the hands, feet and other skeletal structures because it can clearly show even very small bones as well as surrounding tissues such as muscle and blood vessels.

Physicians often use the CT examination to:

• quickly identify injuries to the lungs, heart and vessels, liver, spleen, kidneys, bowel or other internal organs in cases of trauma.
• guide biopsies and other procedures such as abscess drainages and minimally invasive tumor treatments.
• plan for and assess the results of surgery, such as organ transplants or gastric bypass.
• stage, plan and properly administer radiation treatments for tumors as well as monitor response to chemotherapy.
• measure bone mineral density for the detection of osteoporosis.

Risks and Benefits

Benefits:

CT scanning is painless, noninvasive and accurate.

Diagnosis made with the assistance of CT can eliminate the need for invasive exploratory surgery and surgical biopsy.

CT scanning can identify normal and abnormal structures, making it a useful tool to guide radiotherapy, needle biopsies and other minimally invasive procedures.

Risks:

CT does involve exposure to radiation in the form of x-ray, but the benefit of an accurate diagnosis far outweighs the risk. The effective radiation dose from this procedure is about 10 mSv, which is about the same as the average person receives from background radiation in three years.

Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.

Nursing mothers should wait for 24 hours after contrast material (iodine) injection before resuming breast feeding.

The risk of serious allergic reaction to iodine-containing contrast material is rare, and radiology departments are well-equipped to deal with them.