Principles of Viewing in CT

Abstract

The scanner is an assemblage of different elements : X-ray source, detectors, scanning and reconstruction systems, viewing console. This last is somewhat neglected although its role in assuring good resolution is important. Its function is to transform primary numerical information into an anatomical image interpretable by the radiologist. This it does by translating numerical density values into luminance levels on a cathode tube (CRT) which prints the image on ray or polaroid film. Viewing consoles on new-generation scanners usually have a refresh memory which makes them independent of the reconstruction calculator and allows dynamic visualisation in real time. These viewing consoles function with variable viewing “windows” whose clinical interest we now examine.