DefinitionA computed tomography (CT) scan of the arm is an imaging method that uses x-rays to make cross-sectional pictures of the arm.Alternative NamesCAT scan – arm; Computed axial tomography scan – arm; Computed tomography scan – arm; CT scan – armHow 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 machines x-ray beam rotates around you. (Modern “spiral” scanners can perform the exam without stopping.)A computer creates separate images of the arm area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the arm can be created by adding the slices together.You must be still during the exam. Movement can cause blurred images. You may be told to hold your breath for short periods of time.The scan should take only 10-15 minutes.How to Prepare for the Test For some tests, you will need to have a special dye, called contrast, to be delivered into the body before the test starts. Contrast helps certain areas show up better on the x-rays.Contrast can be given through a vein (IV) in your hand or forearm. If contrast is used, you may also be asked not to eat or drink anything for 4-6 hours before the test.Let your doctor know if you have ever had a reaction to contrast. You may need to take medicines before the test in order to safely receive this substance.Before receiving the contrast, tell your health care provider if you take the diabetes drug metformin (Glucophage). You may need to special steps if you are on this medicine.If you weigh more than 300 pounds, find out if the CT machine has a weight limit. Too much weight can cause damage to the scanners working parts.advertisementYou will be asked to remove jewelry and wear a hospital 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 sensation, a metallic taste in the mouth, and a warm flushing of the body. These feels are normal . They will go away within a few seconds.Why the Test is PerformedCT rapidly creates detailed pictures of the body, including the arms. The test may help detect or diagnose:An abscess or infectionThe cause of pain or other problems in the wrist, shoulder or elbow joints (usually when MRI cant be done)A broken boneMasses and tumors, including cancerA CT scan may also be used to guide a surgeon to the right area during a biopsy.Normal ResultsResults are considered normal if no problems are seen in the images.What Abnormal Results MeanAbnormal results may be due to:Abscess (collection of pus)Blood clot in the arm (deep venous thrombosis)Bone tumorsCancerBroken or fractured boneDamage to the hand, wrist, or elbow jointsRisksRisks of CT scans include:Being exposed to radiationAllergic reaction to contrast dyeCT 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 doctor should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.Some people have allergies to contrast dye. Let your doctor know if you have ever had an allergic reaction to injected contrast dye.The most common type of contrast given into a vein contains iodine. A person with an iodine allergy may have nausea or vomiting, sneezing, itching, or hives if given this type of contrast.If contrast is needed, your doctor may give you antihistamines (such as Benadryl) or steroids before the test.The kidneys help remove iodine out of the body. Those with kidney disease or diabetes may need to get extra fluids after the test to help flush the iodine out of the body.Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, let the scanner operator know right away. Scanners have intercom and speakers so the operator can hear you at all times.ReferencesHuber FG. Arm. In: DeLee JC, Drez D Jr, Miller MD, eds. DeLee and Drez?s Orthopaedic Sports Medicine. 3rd ed. Philadelphia, Pa: Saunders Elsevier; 2009:chap 18.Grainger RG, Thomsen HS, Morcos SK, Koh DM, Roditi G. Intravascular contrast media for radiology, CT, and MRI. In: Adam A, Dixon AK, eds. Grainger & Allisons Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 2.advertisementShaw AS, Dixon AK. Multidetector computed tomography. In: Adam A, Dixon AK, eds. Grainger & Allisons Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 4.Review Date:1/17/2013Reviewed By:C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.