Digital radiography.

A quantitative comparison of the digital techniques reviewed in section 4.1-4.7 is difficult, for two reasons. Firstly, various authors have used slightly different techniques for assessing aspects of imaging performance (e.g. a variety of test objects for, and definitions of, spatial resolution). Secondly, with all imaging systems there exists an inter-relationship between spatial resolution, image acquisition time, image noise and dose. Some authors have chosen to emphasise one feature at the expense of others. Arnold (1982), in an overview of digital radiographic technology at that time, also noted the lack of standardisation of measurement techniques and exposure conditions, but nevertheless attempted a quantitative comparison of some aspects of digital radiographic systems with screen-film radiography and CT. The continuing developments in the field since then make a brief quantitative intercomparison of dubious value. Nevertheless, a qualitative summary of point, line and area exposure techniques is given in table 2 which incorporates many of the comments made by Arnold et al (1986) in a similar summary of digital radiographic systems.