CT imaging, sometimes called a CAT Scan, is an advanced imaging test that helps physicians diagnose and treat many medical conditions. CT Scans use a series of X-ray views taken from different angles to produce multiple images of the inside of the body. A computer then joins these images together in cross-sectional and 3-D views of the area. CT Scans are very effective in viewing internal organs, bone, soft tissue and blood vessels to provide greater clarity than conventional X-ray exams.
What is the exam like?
The CT Scanner is a large machine with a hole in the center. Since X-rays have difficulty passing through metal, you will need to remove jewelry from the area being scanned. You will be asked to lie on a table that slides into the center of the machine. Depending on the study being done, you may need to lie on your stomach. Usually, you will lie on your back. The scan itself is painless.
Once you are inside the scanner, the machine's X-ray beam rotates around you. You must be still during the exam, because movement causes blurred images. You may be asked to hold your breath for short periods of time and you will hear clicking and whirring noises.
Generally, complete scans take only a few minutes. The newest multi-detector scanners can image your entire body, head to toe, in less than 30 seconds.
Certain CT exams require a special dye, called contrast, to be delivered into the body before the test starts. Contrast highlights specific areas inside the body, which creates a clearer image. Depending on the type of examination, the contrast may be swallowed, and or, injected through an intravenous line (IV). Contrast given through an IV may cause a slight metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds. If contrast is used, you may also be asked not to eat or drink anything for 4-6 hours before the test.
How is the test performed?
A computer takes the scans and creates several individual images, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of organs can be created by stacking the individual slices together. CT images are stored as electronic data files and are reviewed on a computer. A radiologist interprets these images and sends a report to your doctor.
What are the risks?
CT Scans and other X-rays are strictly monitored and controlled to make sure they use the least amount of radiation possible. CT Scans do create low levels of ionizing radiation. However, the risk associated with any individual scan is very small. The risk increases as numerous additional studies are performed. In most cases, the benefits greatly outweigh the risks.
An abdominal CT Scan is usually not recommended for pregnant women, because it may harm the unborn child. Women who are or may be pregnant should speak with their health care provider to determine if ultrasound can be used instead.
The contrast that is given intravenously contains iodine. The kidneys help filter the iodine out of the body. Therefore, those with kidney disease or diabetes should receive plenty of fluids after the test, and be closely monitored for kidney problems. If you have diabetes or are on kidney dialysis, talk to your healthcare provider before the test about your risks.
Very rarely, the IV contrast may cause allergic reactions in some people. Most reactions are mild and may include sneezing and itching. If you have any trouble difficulty during the test, you should notify the CT technologist immediately. Scanners come with an intercom and speakers, so the tech can hear you at all times. Very rarely, a life-threatening allergic response may be caused by the contrast.