Physical characteristics of four roentgenographic chains proposed for chest radiography

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Abstract
Four types of roentgenographic chains were studied as follows: the ordinary grid technique with 10 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. Effect of motion unsharpness on resolution was examined theoretically. RMS [roat mean square] noise 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 1/3 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 [human] chest radioagraphy.

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