Concept of windowing

·         Concept of windowing:  to manipulate the contrast of an image for example a CT image.

·         Window level:  CT that corresponds to the centre CT number of the window.

·         Window width:  The number of CT numbers that covers the grey scale range from black to white  --  CT numbers between P1 and P2.  CT numbers above P2 white and CT numbers below P1 is black.

·         A narrow window width produces a high contrast image.