Objective performance measurements versus perceived image quality in intensified fluoroscopic or photospot images

The relationship between perceived image quality and measurable performance parameters of an intensified fluoroscopic image, viewed via a TV monitor or recorded on 105mm film, was investigated. Four specially manufactured image tubes, differing significantly in x-ray absorption efficiency, spatial resolution, and/or contrast resolution, were studied. Quantitative measurements of tube performance included the conversion factor, the quantum detection efficiency, the limiting resolution, the contrast ratio, and the contrast-detail characteristics. An assessment of the quality of clinical images was made by two radiologist-observers, working independently and without knowledge of any quantitative results. The observers were asked to rate the noise, lag, resolution, and contrast of the images during a variety of fluoroscopic procedures on each tube. While general agreement was found between the quantitative measurements and the radiologists' perceptions of image quality, the noise and contrast performance of an intensifier had greater influence on the radiologists' judgment of image quality than did resolution.