Digital radiology: an opportunity for quantitative measurement

A digital detector provides numerical information at each pixel. This value may be difficult to be interpreted quantitatively. In this paper, the main factors to be considered during physical interpretation are reviewed: beam-hardening effect, scattering diffusion, type of detector. Some of them induce degradation on the digital radiograph while others modify the nature of available information. Signal-to-noise ratio should be taken into account, and compared to the accuracy required by the inspection process. Different existing methods are discussed for scatter correction. Then we analyse different techniques of digital radiography based on the quantitative aspect - thus assuming good accuracy of radiographs values: tomography and 3D techniques, and dual-energy approaches. Finally we evoke emergent detectors based on semi-conductors, which are energy selective photon-counters, thus offer new opportunities in terms of information processing. (authors)