Computed Tomography or Computerized tomography (CT) is a type of medical examination that makes use of X-rays and computer processing to create cross sectional images of the body. CT scan has also been known as Computerized Axial Tomography scan (CAT scan).
A motorized X-ray source rotates around the circular opening called the gantry, of a donut-shaped structure in the Computed Tomography scanner. During a CT scan, the subject lies on a surface that slowly moves through the gantry while the X-ray source rotates around in the structure, shooting narrow beams of X-rays through a section of the subject's body. Digital X-ray detectors are used in the CT scanners, which are located directly opposite to the X-ray source. The detectors pick up the X-rays on their way out of the subject. Many images taken at different angles are collected during one complete rotation and are transmitted to a computer. For each rotation, the CT computer reconstructs the image data collected into one or multiple cross-sectional images of the internal organs or tissues using complex mathematical formulae. Sometimes, CT involves the use of a contrast (imaging) agent, or "dye." The dye may be given by mouth, injected into a vein, given by enema, or given in all three ways before the procedure. The contrast dye highlights specific areas inside the body, resulting in clearer pictures.
Radiation exposure
During a CT scan, you're briefly exposed to ionizing radiation. The amount of radiation is greater than you would get during a plain X-ray because the CT scan gathers more detailed information. CT scans have many benefits that outweigh this small potential risk.
Harm to unborn babies
Tell your doctor if you're pregnant. Although the radiation from a CT scan is unlikely to injure your baby, your doctor may recommend another type of exam, such as ultrasound or MRI, to avoid exposing your baby to radiation.
