Physical characteristics of four roentgenographic chains proposed for chest radiography

Four types of roentgenographic chains have been studied in the present work: the ordinary grid technique with 1 screen-film combinations, the air gap technique with 8 screen-film combinations, the roentgen photofluorography (RP technique) and the spotfilm technique. To study resolution and contrast properties a gold plate was radiographed in a 20 cm thick water phantom and the equivalent passband and the inherent subject contrast were calculated. The effect of motion unsharpness on resolution was examined theoretically. The RMS nose and the speed of each technique were evaluated. The air gap technique proved to be a good alternative to the ordinary grid technique. Rare earth screens decrease the radiation dose to at least one third of that of a medium-speed film/calcium tungstate screen combination without noticeably impairing resolution, contrast or noise properties, but reducing motion unsharpness considerably. Differences between various screen-film combinations of equal speed were not very marked. The RP technique proved to be poorest in almost all respects. The spotfilm technique seems worth developing for chest radiography.