(H) The Hounsfield scale displays radiodensity in a linear scale of gray shades expressed in Hounsfield units (HU). The Hounsfield scale is a quantitative transformation of the attenuation coefficient.
The Hounsfield value -1000 is defined as the radiodensity of air, 0 H that of distilled water at standard pressure and temperature, and denser tissues like for example cranial bone can reach 2000 H. The radiation attenuation of dental fillings or artificial implants depends on atomic number of the elements used. Titanium usually has an amount of +1000 HU. Iron steel can have a density greater than the highest range (traditional 3095 H) covered by the standard Hounsfield scale of a CT scanner. Areas with attenuation coefficients that exceed the scale's maximum are white areas in which no detail is visible.
Some CT machines are relatively tolerant, precise representing regions with very high densities. Sometimes, an option is available to select an extended CT number scale.

(Computed tomography number) The CT number is a selectable scan factor based on the Hounsfield scale. Each elemental region of the CT image (pixel) is expressed in terms of Hounsfield units (HU) corresponding to the x-ray attenuation (or tissue density).
CT numbers are displayed as gray-scale pixels on the viewing monitor. White represents pixels with higher CT numbers (bone). Varying shades of gray are assigned to intermediate CT numbers e.g., soft tissues, fluid and fat. Black represents regions with lower CT numbers like lungs and air-filled organs.

A display is a computer monitor that shows the processed data from the scanned area. Displays can be black-and-white or color, small or large depending upon the model and price of the machine.

See also Display Field of View, Display Matrix, Window Width, Bit Range, Hounsfield Scale, Interpolation, Minimum Intensity Projection, and Printer.

(HU) [CT scanner display unit] The arbitrary scale is defined by air, which has a CT number of -1000 HU, and water, with a CT number of 0 HU. It is named after Sir Godfrey Hounsfield, who developed the first clinical CT scanner.

See also Hounsfield Scale.