CT (computed tomography), sometimes called CAT (computed axial tomography) scan, uses a rotating focused x-ray beam guided by a computer to produce complex detailed images showing a “cross-section” of body tissues and organs. CT imaging is particularly useful because it can show several types of tissue, such as lung, bone, soft tissue and blood vessels, with great clarity. Using specialized equipment and expertise to create and interpret CT scans of the body, radiologists can more easily
CT is one of the best tools for studying the chest and abdomen. It is 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. CT can clearly show even very small bones as well as surrounding tissues such as muscle and blood vessels. This makes it invaluable in diagnosing and treating spinal problems and injuries to the hands, feet and other skeletal structures. CT can also play a significant role in the detection, diagnosis and treatment of vascular.
- CT scanning offers detailed views of many types of tissue including the lungs, bones, soft tissues and blood vessels.
- CT scanning is painless, noninvasive and accurate.
- CT examinations are fast and simple.
- CT scanning can identify normal and abnormal structures, making it a useful tool to guide radiotherapy, needle biopsies and other minimally invasive procedures.
- CT does involve exposure to radiation in the form of x-rays, 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. Special care is taken during x-ray examinations to minimize exposure.
- Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.
- Nursing mothers should wait 24 hours after contrast 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.
How should I prepare for the CAT scan?
You should wear comfortable, loose-fitting clothing for your CT exam. Metal objects can affect the image, so avoid clothing with zippers and snaps. You may also be asked to remove hairpins, jewelry, eyeglasses, hearing aids and any removable dental work, depending on the part of the body that is being scanned.
If you are having a CT of the abdomen or pelvis, please arrive 1 hour prior to your exam to drink the oral contrast. In addition, do not eat or drink for 4 hours prior to the exam. You may have small amounts of water, if needed, to take medications only.
If you are having any other type of CT exam, please arrive 30 minutes early. Please do not eat for one hour prior to your exam.
Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.
NEED SPECIFIC PREPS FOR SPECIFIC EXAMS
What should I expect?
The technologist begins by positioning the patient on the CT table. The patient’s body may be supported by pillows to help hold it still and in the proper position during the scan. As the study proceeds, the table will move slowly into the CT scanner. Depending on the area of the body being examined, the increments of movement may be so small that they are almost undetectable or large enough that the patient feels the sensation of gentle motion.
A CT examination often requires the use of different contrast materials to enhance the visibility of certain tissues or blood vessels. The contrast material may be swallowed, injected through an IV directly into the blood stream or administered by enema, depending on the type of examination. Some patients find the taste of the oral contrast material mildly unpleasant but most can easily tolerate it. Before administering the intravenous contrast material, the technologist will ask whether the patient has any allergies, especially to medications or iodine, and whether the patient has a history of diabetes, asthma, a heart condition, kidney problems or thyroid conditions. These conditions may indicate a higher risk of reaction to the contrast material or potential problems eliminating the material from the patient’s system after the exam. Some people report feeling a flush of heat and sometimes a metallic taste in the back of the mouth. These sensations usually disappear within a minute or two. Some people experience a mild itching sensation. If it persists or is accompanied by hives (small bumps on the skin), the itch can be treated easily with medication. In very rare cases, a patient may become short of breath or experience swelling in the throat or other parts of the body. These can be indications of a more serious reaction to the contrast material that should be treated promptly, so tell the technologist immediately if you experience these symptoms. Fortunately, with the safety of the newest contrast materials, these adverse effects are very rare.
A CT examination usually takes five minutes to half an hour. When the exam is over the patient may be asked to wait until the images are examined to determine if more images are needed.