Sensitivity of visual targets for display quality assessment

Assessing the image quality of display devices is becoming an important concern for radiology departments with large numbers of widely distributed image displays. Methods commonly used for laboratory measurements are too costly and cumbersome for routine quality assessment, however, methods that rely on visual assessment of currently available test targets may not have adequate sensitivity. The purpose of this paper is to quantify the sensitivity of commonly used test targets for visual assessment of medical display devices with well-defined changes in sharpness and nose. Two test targets methods were selected form those that have been used for visual assessment of image displays. For each, the assessment is a measure of the size and contrast of the smallest visible pattern in the target. Computer simulation was used to produce images of each of the targets having known sharpness and nose degradation. Viewers were trainee in the use of each target, then asked to score a randomly ordered set of simulation-degraded target images. These data were approximately analyzed for each method and the result evaluated with standard statistical methods. Assessments were found to correlate with sharpness and noise. However, the sensitivity of both targets for single-stimulus assessment was found to be adequate. The practical utility of these methods must therefore be questioned.