EVALUATION OF RESOLUTION AND SENSITOMETRIC CHARACTERISTICS OF AN ASYMMETRIC SCREEN-FILM IMAGING-SYSTEM

The authors compared asymmetric and conventional screen-film systems for chest radiography. The new imaging system, with asymmetric construction of the screens and film, has image quality characteristics substantially different from those of available screen-film combinations. This asymmetric screen-film system consists of a thin (high-resolution) front screen and a high-contrast emulsion, a thick (lower-resolution) back screen and a low-contrast emulsion, and technology that reduces the crossover exposure and prevents light from the front screen from exposing the back emulsion and vice versa. With this system, density, contrast, and resolution can be increased in selected regions while maintaining density and contrast in the rest of the image. Also, the resolution of this system varies as a function of density. Preliminary image quality and sensitometric studies indicate the new system is superior for chest radiography because it provides better visualization of mediastinal, retrocardiac, and diaphragmatic regions while yielding better contrast and resolution in lung parenchyma.