A Gray scale inverter for use with CT scanners and other imaging systems

In CT scanners and other imaging systems clinical images are often presented on a TV monitor. Their permanent recording is frequently achieved by photographing them with transparency type film but it would be convenient if the image produced on the film looked like that on the monitor. Electronically inverting the video signal applied to the cathode ray tube prior to photography gives a light-to-dark reversal of the display. When the film produces a second reversal, the resulting transparency has an appearance similar to the image on the viewed display. (UK)