Contrast-detail-dose and dose efficiency analysis of a scanning digital and a screen-film-grid radiographic system

The purpose of this study is to examine the diagnostic potential of a scanning digital radiography (SDR) system currently used clinically as a CT localization device. The technique of contrast-detail-dose analysis is used to compare the low-contrast sensitivity and dose efficiency of an SDR unit with standard radiography (SR). The theory of threshold perceptibility in both digital radiography and SR is described, including the effects of scattered radiation and antiscatter devices, object attenuation, geometry, system image processing, and recorder quantum efficiency. The concept of dose efficiency is defined and derived from the contrast-detail-dose data. The SDR system is shown to operate with a threshold signal-to-noise ratio of 7.3 +/- 1.2 for large area detection (d greater than or equal to 2 mm); to be relatively scatter-free; and to be as much a 100x more dose efficient than SR for visualization of large low contrast objects (C less than or equal to 0.04, d greater than or equal to 2 mm).