What is a CT scan?

A CT scan is an imaging test that uses X-rays and a computer to take cross-sectional pictures of the body. A CT scan, also called a CAT (computed axial tomography) scan, makes layered images of an entire body area. The images are similar to slices of a loaf of bread. CT scans are more detailed than regular X-rays They help doctors diagnose and treat many diseases, disorders and conditions. 

A CT scan is a painless, noninvasive medical test. It makes images of any organ or body part. A CT scan is only one method of diagnosing and monitoring many diseases, disorders and conditions. Discuss all your diagnostic and monitoring options with your doctor to understand which options are best for you.

Types of CT scans

Standard CT scans can make pictures of almost any body structure using only the CT scan machine. Your doctor may add a contrast agent or dye or use specialized CT scan machines and techniques to make clearer or more detailed images. Specialized CT scans include:

  • Cardiac CT makes detailed images of the heart and often involves injecting a contrast dye into a vein.
  • Coronary calcium scan looks for calcium deposits in the coronary (heart) arteries. A coronary calcium scan uses medication to slow your heart and an EKG machine to record your heart’s electrical activity during the scan. 
  • CT angiography makes detailed images of blood vessels and tissues by injecting a dye through a small tube (catheter) inserted into a vein.
  • CT enterography makes detailed pictures of the small intestine using a contrast dye that you drink.
  • CT colonography (virtual colonoscopy) makes detailed pictures of the inside of the large intestine. It involves pumping carbon dioxide gas through a tube in the rectum to expand the large intestine for better viewing.
  • Multislice CT or multidetector CT makes thinner imaging slices in a shorter period than a traditional CT scan. This creates images with more detail.
  • SPECT (single-photon emission computed tomography) shows the function of organs. A SPECT scan is a type of nuclear imaging test that uses a radioactive substance and a special camera combined with CT scanning to create 3-D pictures. 
  • PET/CT (positron emission tomography/computed tomography) is used to diagnose or determine the severity of many diseases, such as cancer. PET/CT is a type of nuclear imaging test that makes images using a radioactive substance and a special camera combined with CT to create detailed pictures. 

Why is a CT scan performed?

Your doctor may recommend a CT scan to screen, diagnose, and monitor the progress of many diseases, disorders and conditions in almost any part of the body. Examples include:

  • Aneurysms including brain aneurysms and aortic aneurysms in the abdomen or chest
  • Atherosclerotic disease including coronary artery disease and peripheral artery disease   
  • Blood clots including clots that cause pulmonary embolisms and ischemic stroke 
  • Chronic diseases including osteoporosis and arthritis
  • Congenital malformations including birth defects of the heart, kidneys, brain, and blood vessels
  • Infections including abscesses and acute appendicitis 
  • Inflammatory bowel disease including Crohn’s disease and ulcerative colitis
  • Injuries and trauma including broken bones and organ injury such as a ruptured pancreas or brain hematoma
  • Internal bleeding including hemorrhagic stroke and bleeding due to trauma 
  • Tumors and cancer including benign masses, lymphomas, and cancers of organs such as the kidney, brain, liver, pancreas and colon  

CT scans are also used to:

  • Confirm a diagnosis of symptoms including facial drooping, slurred speech, changes in vision, and abdominal and pelvic pain 
  • Guide procedures including biopsies and drainages of abscesses
  • Monitor treatments including the results of surgery, chemotherapy, and radiation therapy
  • Plan surgery and other treatments including chemotherapy, radiation therapy, and cancer, tumor, and organ transplant surgeries

Who performs a CT scan?

A radiologic technologist supervised by a radiologist