[Influence of tandem optics and television tube of modern digital fluoroscopy equipment on image quality]. / Einfluss von Tandemoptik und Fernsehaufnahmeröhre moderner Durchleuchtungsanlagen auf die Bildqualität.

ABSTRACT

The influence of the tandem optics and the TV-tube to the image quality of 1k- and 2k-radiographs of a modern fluoroscopy equipment should be assessed on the basis of objective parameters and clinical requirements. Radiographs of different phantoms with 1k- and 2k-image matrix, different illumination point corrections (IPC) and signal gray levels were taken, examined and evaluated, in order to determine the objective image parameters and the clinical relevancy of these parameters. On the one hand, the digital images data could be used directly for evaluation; on the other hand, the radiographs could be visually evaluated by experienced radiologists within the framework of a blind study. The IPC is controlled by the aperture of the iris diaphragm and the insertion of a neutral gray filter in the tandem optics. The larger the aperture of the iris diaphragm (at constant image receiver dose) the higher were gradation, signal to noise ratio (SNR) and image homogeneity. Furthermore, the larger the aperture, the lower was the square wave response function (SWRF). The insertion of a gray filter in the tandem optics decreases gradation, SNR and homogeneity, and improves the SWRF.