Visual perception and image display terminals.

It should be clear that there is no prescription for an ideal picture terminal or for an ideal image work station. Image informativeness, the ability to transmit the relevant diagnostic information to the viewer, is the most important medical consideration that has an impact on the individual patient, but short of doing extensive observer performance studies, there is no way of being absolutely sure that any given display method is transmitting visual information optimally. Certain principles are clear, however. Pixel clutter should be eliminated, and stochastic noise should be minimized. Contrast should be maximized, but there must be a rational relationship between the intensity of the stored image and the luminance of the displayed image. In my opinion, there should be a monotonically increasing relationship. Cross-sectional images and projection images, especially those of large body parts such as the chest, may not be analogous with regard to the method for contrast enhancement. Windowing, which works well for cross-sectional images, may produce bizarre appearances in projection images because of the nonlinearities in image intensity that are caused by overlapping structures. There is little objective information about the best format for displaying single images of large body parts or multiple images of any type. Although the development of picture terminals will undoubtedly be driven by economics and by the available technology, it might prove very fruitful to make the effort required to define the specifications for a picture terminal on the basis of the optimal transfer of visual information. Fortunately, people are highly adaptable and can learn to use almost anything to their advantage, but it would be a pity if digital image readers of the future have to decide which terminal or station is best on the basis of image aesthetics rather than diagnostic performance.