8-bit or 11-bit monochrome displays-which image is preferred by the radiologist?

Vendors of medical displays promise a better diagnostic performance using 10- or 11-bit instead of 8-bit monochrome displays. We measured the gain of "Just Noticeable Difference" (JND) steps using high grayscale resolutions and evaluated the preference of radiologists regarding different aspects of image quality. The amount of JND steps was measured on a display using 8-, 10- and 11-bit Look Up Tables (LUT). Radiological images were presented simultaneously using an 8-bit and an 11-bit LUT, radiologists where asked to determine the better image presentation regarding quality parameters like sharpness, contrast and detectability of details. The 10-bit technology realized more than twice the number of JND steps compared to an 8-bit LUT, an 11-bit LUT presented only few additional JND steps. The radiologists did not attest the higher grayscale resolution a better image quality, they regarded the 8-bit technology to show a better sharpness and contrast, although this had no impact on the detectability of details. Our measurements confirmed that the higher grayscale resolution results in a more complete visualization of image information. But radiologists partially judged this as a lack of sharpness and contrast and generally preferred the 8-bit display.