Scanner Facts



  • Scanners are electronic devices that move backwards and forwards in lines in order to build up a picture.
  • Image scanners are used to convert pictures and other material into a digital form for computers to read.
  • A photoelectric cell in the scanner measures the amount of light reflected from each part of the picture and converts it into a digital code.
  • Various scanners are used in medicine to build up pictures of the inside of the body. They include CT scanners, PET scanners and MRI scanners.
  • CT stands for computerized tomography. An X-ray beam rotates around the patient and is picked up by detectors on the far side to build up a 3-I) picture.
  • PET stands for Positron Emission Tomography. The scanner picks up positrons (positively charged electrons sent out by radioactive substances injected into the blood.
  • PET scans can show a living brain in action.
  • MRI stands for Magnetic Resonance Imaging.
  • An MRI scan works like CT scans but it uses magnetism, not X-rays. The patient is surrounded by such powerful magnets that all the body’s protons line up.
  • The MRI scan begins as a radio pulse that knocks the protons briefly out of alignment. The scanner detects radio signals sent out by the protons as they snap back into line. This PET scan shows a monkey’s brain from above displays on a monitor.