CAT scan; Computed axial tomography scan; Computed tomography scan DefinitionA computed tomography (CT) scan is an imaging method that uses x-rays to create pictures of cross-sections of the body. Related tests include:
How the Test is PerformedYou will be asked to lie on a narrow table that slides into the center of the CT scanner. Once you are inside the scanner, the machine's x-ray beam rotates around you. Modern spiral scanners can perform the exam without stopping. There is very little noise. A computer creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or copied to a disk. Three-dimensional models of the body area can be created by stacking the slices together. You must stay still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time. Complete scans most often take only a few minutes. The newest scanners can image your entire body in less than 30 seconds. How to Prepare for the TestCertain exams require a special dye, called contrast, to be delivered into your body before the test starts. Contrast helps certain areas show up better on the x-rays. Let your health care provider know if you have ever had a reaction to contrast. You may need to take medicines before the test in order to avoid another reaction. Contrast can be given several ways, depending on the type of CT being performed.
If contrast is used, you may also be asked not to eat or drink anything for 4 to 6 hours before the test. Before receiving IV contrast, tell your provider if you take the diabetes medicine metformin (Glucophage). People taking this medicine may need to stop temporarily. Also let your provider know if you have any problems with your kidneys. The IV contrast can worsen kidney function. Find out if the CT machine has a weight limit if you weigh more than 300 pounds (135 kilograms). Too much weight can damage the scanner. You will need to remove jewelry and wear a gown during the study. How the Test will FeelSome people may have discomfort from lying on the hard table. Contrast given through an IV may cause a slight burning feeling, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds. Why the Test is PerformedA CT scan creates detailed pictures of the body, including the brain, chest, spine, and abdomen. The test may be used to:
Normal ResultsResults are considered normal if the organs and structures being examined are normal in appearance. What Abnormal Results MeanAbnormal results depend on the part of the body being studied. Talk to your provider about questions and concerns. RisksRisks of having CT scans include:
CT scans expose you to more radiation than regular x-rays. Having many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your provider should weigh this risk against the value of the information that will come from a CT scan. Most new CT scan machines have the ability to reduce the radiation dose. Some people have allergies to contrast dye. Let your provider know if you have ever had an allergic reaction to injected contrast dye.
Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, tell the scanner operator immediately. Scanners come with an intercom and speakers, so the operator can hear you at all times. ReferencesBlankensteijn JD, Lely RJ. Computed tomography. In: Sidawy AN, Perler BA, eds. Rutherford's Vascular Surgery and Endovascular Therapy. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 29. Levine MS, Gore RM. Diagnostic imaging procedures in gastroenterology. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 124. Van Thielen T, van den Hauwe L, Van Goethem JW, Parizel PM.Current status of imaging of the spine and anatomical features. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 47. | ||
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Review Date: 7/5/2022 Reviewed By: Jason Levy, MD, FSIR, Northside Radiology Associates, Atlanta, GA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. View References The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited. | ||
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CT scan
