Image Acquisition

Digital detectors offer higher quantum efficiency and higher resolution than traditional screen-film receptors [166]. These will translate into both lower dose and improved image quality mammograms.

Digital detectors for mammography can be categorized as indirect or direct conversion detectors according to how the X-ray is captured. In indirect conversion methods (the earliest ones) the energy of the X-rays is captured by a scintillator which converts it to light. Subsequently, this light is captured by an array of thin-film diodes which convert it to electronic signal which, in turn, is captured using thin-film transistors. The main problem of these systems is that the created light by the scintillator scatters to its neighbourhood, and the same X-ray is captured by different transistors. On the other hand, in direct conversion systems the same photoconductor that captures the X-ray is able to directly generate an electronic signal. Thus, scattering is less severe in these systems.

Berns et al. [10] compared the acquisition time between screen-film and digital mammography acquisition. While the former averaged $21.6$ minutes, the latter averaged $14.1$ minutes, which is a highly significant $35\%$ shorter time. However, the total interpretation time of the images by the experts averaged $1.4$ minutes for screen-film mammography and $2.3$ minutes for digital mammography, a highly significant $57\%$ longer interpretation time.