Which factor influences the contrast of an image display on a viewing monitor?

The correct choice relates to how window width affects the contrast of an image on a viewing monitor. In medical imaging, window width determines the range of pixel values that are displayed in various shades of gray; a narrower window width results in a higher contrast image, while a wider window width provides lower contrast. By controlling the window width, the radiologist can emphasize specific tissue types or pathologies within the image, making it easier to distinguish between different structures based on their varying densities and intensities.

For example, if the window width is set narrow, only a small range of intensity levels will be shown, thus enhancing the differences between adjacent tissues and allowing for better detection of abnormalities. Conversely, broader settings can wash out these differences, potentially obscuring critical details.

Window level, while also important, adjusts the midpoint of the gray scale rather than affecting contrast directly. Signal intensity and proton density are important parameters in imaging, but they influence the quality and formation of an image rather than the direct contrast adjustments on the display monitor.