windowing

n.

a technique of image manipulation commonly used in cross-sectional imaging to manipulate a grey scale image. Typically there is too much data obtained in a scan to see on a single image: the radiologist therefore chooses the window level centred on the density of the tissue of interest and a window width wide enough to include the densities of all the tissues that need to be seen. Tissues denser than this window usually appear white, and tissues darker appear black. Sometimes several different images of the same scan are required at different window settings to see adequately all the necessary detail (for example, window settings to observe the lung are different from those for the bones or the soft tissues in the chest on CT). See also Hounsfield unit.