CT Scan OverviewComputed Axial Tomography
Computed Axial Tomography ("CT" or "CAT" scan) is a way of looking inside your body using a special camera. During a CT exam the scanner takes multiple cross-section "pictures" (like slices in a loaf of bread). With the help of a computer, pictures are created which show internal body parts in much greater detail than standard X-ray films. These images greatly improve the doctor's ability to diagnose a medical condition.
CT scans have a number of uses. In cancer detection, computed tomography is used to scan for abnormal masses which might be malignant tumors (cancers). CT scans can show the size and shape of a tumor, its precise location in the body and whether it's solid or hollow. Although a CT scan is sometimes able to tell the difference between a benign (non-cancerous) or malignant (cancerous) tumor, the final diagnosis is made by a biopsy or another test. When a needle biopsy is performed for cancer diagnosis, CT scanning also can be used to guide the insertion of the biopsy needle into precisely the right location for sampling a tumor. CT scans are also used for the detection of abscesses, strokes, head injuries, bleeding inside the skull and many other conditions. In obese patients, CT scanning may be more useful than ultrasound, since large amounts of body fat can interfere with ultrasound waves.
The CT scanner contains a large donut-shaped ring that your body slowly passes through on a moveable table. As you pass through the ring, the scanner takes a complete 360- degree picture of you that is sent to its computer. Then the mechanical table moves a small distance - less than half-an-inch - positioning you for the next picture. These pictures are reconstructed by the computer to form a complete image of your internal anatomy.
To make a clearer picture of certain parts of your body, some CT scans require the use of contrast materials, which are substances showing up as pure white on the X-ray. Two types of contrast materials used are barium, which you usually drink, and iodine, which is usually injected by means of an I.V. (intravenous line).
Benefits of a CT Scan include
- An experienced radiologist can diagnose many causes of abdominal pain with nearly 100 percent accuracy by viewing a CT scan. This can mean faster treatment and often eliminates the need for additional, more invasive diagnostic procedures.
- CT scanning offers detailed views of many types of tissue, including the lung, bones, soft tissues and blood vessels.
- CT scanning can identify both normal and abnormal structures, making it a useful tool to guide radiotherapy, needle biopsies and other minimally invasive procedures.
- CT scanning is painless, noninvasive and accurate.
- The exam shows changes in bone better than any other imaging method.
- CT Angiography can be used to examine blood vessels in many areas of the body including the brain, kidneys, pelvis, and the arteries serving the lungs. The procedure is able to detect narrowing of arteries in time for corrective surgery to be done.
Risks of CT Scans include:
- CT involves some exposure to radiation in the form of x-ray, but the benefit of an accurate diagnosis far outweighs the risk. The typical radiation dose from a CT exam is about the same as the amount of natural background radiation received over a year's time.
- Special care is taken during x-ray examinations to ensure maximum safety for the patient by utilizing low radiation dose techniques. Women should always inform their doctor or x-ray technologist if there is any possibility they are pregnant.
- Nursing mothers should wait for 24 hours after contrast material injection before resuming breast-feeding.
- Serious allergic reaction to iodine-containing contrast material is rare, and the radiology department is well equipped to deal with them.
- If a large amount of x-ray contrast leaks out under the skin where the IV is placed, skin damage can result. If you feel any pain in this area during contrast injection, you should immediately inform the technologist.
- CT Angiography should be avoided in patients with kidney disease or severe diabetes because x-ray contrast can harm kidney function.
What You Should Know
You will be asked to change into a gown for most procedures. Avoid clothing with zippers and snaps as metal objects can affect the image. You may be asked to remove hairpins, jewelry, eyeglasses, hearing aids and any removable dental work that could obscure the images. You also may be asked to refrain from eating or drinking anything prior to certian CT exams. Follow the instructions given by your physician's office or technologist. Women should always inform their doctor or X-Ray technologist if there is any possibility that they are pregnant.
The test itself is painless. You will be asked to lie quietly during the study. Depending on the type of study being done, you may be injected with, or be asked to drink, contrast material.
Contrast agents contain iodine, which causes an allergic reaction in some individuals. Be sure to tell the technologist, nurse or radiologist if you have had an allergic reaction to these agents before, or if you have any other allergies. You may have been given contrast material earlier as part of a CT scan, a kidney x-ray (also called an IVP), or a heart or blood vessel catheterization (also called an angiogram).
After the test, most patients are able to return to normal activities immediately.
At St. Rita's, we have a board certified radiologist on site daily. Your exam will be read and a report will be phoned, faxed, mailed or delivered electronically to your physician. He or she will share the results with you.