AAPM/RSNA tutorial on equipment selection: PACS equipment overview: display systems

Abstract

Display systems are key components of the digital radiology department. Current display systems for medical imaging are based on cathode-ray tubes (CRTs) or active-matrix liquid crystal displays (AMLCDs). The CRT is a cathodoluminescent display: Light is generated by exciting a luminescent material with energetic electrons. AMLCDs are light-modulating devices that form the image in the screen by controlling the transparency of individual display pixels. Many image quality aspects of CRTs are determined by the way the pixel luminance is generated in the cathodoluminescent screen. The resolution properties of AMLCDs are much better than those of CRTs. In CRT devices, phosphor granularity and raster scanning patterns are the main components of spatial noise. In AMLCDs, the most notable feature of the noise characteristic is the subpixel structure of complex pixel designs used in medical displays. The small-spot contrast of CRTs is dominated mainly by veiling glare and reflections of ambient illumination. In addition to display reflectance, the contrast of medical AMLCDs is affected by crosstalk and by variations of the luminance at off-normal viewing angles.