CT Scan

What Is a CT Scan?

Joseph Bennington-Castro
By Medically Reviewed by 
Reviewed:
Medically Reviewed

CT scans, or 'CAT scans," produce highly detailed X-ray images of your body to reveal numerous health issues.

Computed tomography (CT) is a diagnostic procedure that's sometimes referred to as computed axial tomography, or a "CAT scan."

CT scans use X-rays to produce 2D cross-sectional images, or slices, of the body's bones, soft tissues, and blood vessels.

Using computers, these images can be "stacked" to create 3D models of specific areas of the body.

Unlike traditional X-ray imaging technologies, which use a fixed X-ray source, CT scanners use a motorized X-ray source that rotates around the body, allowing for more detailed images.

CT Scan Uses

Physicians may order CT scans to:

  • Examine internal and bone injuries from vehicle accidents or other trauma
  • Diagnose spinal problems and skeletal injuries
  • Detect osteoporosis
  • Detect many different types of cancers and determine the extent (spread) of the tumors
  • Locate infections
  • Look for injuries, stroke-causing clots, hemorrhaging, and other issues in the head
  • Image the lungs to reveal blood clots in the lungs' vessels, excess fluid, pneumonia, and chronic pulmonary obstructive disease (COPD)
  • Determine the cause of chest or abdominal pain, difficulty breathing, and other symptoms
  • Diagnose dangerous vascular diseases that can cause stroke, kidney failure, and death

Additionally, CT scans are used to assist with biopsies and other medical procedures, and help with treatment planning for organ transplants, gastric bypass, and cancer, among other things.

CT Scan Procedure

The procedure begins with you lying on a narrow table that slides in and out of the center of the CT scanner.

The X-ray source and X-ray detectors are located on opposite sides of the scanner's ring, or gantry.

During the scan, the gantry will rotate around you, sometimes while you move through the scanner's tunnel.

The source sends X-rays through your body, which the detectors pick up and a computer translates into images.

To image soft tissues, your physician may use a special dye (called a contrast dye) during the test to help visualize these body parts, which may otherwise be difficult to see.

The contrast may be ingested, given via IV, or administered rectally with an enema.

CT Scan Risks

Some people are allergic to the ingredients in the contrast dye, resulting in nausea and vomiting, sneezing, itching, or hives.

Anaphylaxis, a life-threatening allergic reaction, or kidney failure may also occur.

Also, CT scans produce far more ionizing radiation than traditional X-rays.

A single abdominal scan, for example, delivers up to 400 times the radiation of a single chest X-ray, according to the National Institute of Biomedical Imaging and Bioengineering.

Rare complications of this radiation include:

  • Increased lifetime risk of cancer
  • Skin reddening and tissue injury
  • Hair loss
  • Cataracts
  • Birth defects if used during pregnancy