ABSTRACT
From the first radiograph ever produced of Frau Röntgen's hand (Röntgen 1896a,b) (see Section II, Chapter 17 of this book), to most of the X-ray detectors commonly used today in medical imaging, X-ray detection devices are based on energy integrating technologies (Yaffe and Rowlands 1997; Rowlands and Yorkston 2000; Russo 2004; Esposito et al. 2011a; Esposito et al. 2014). When energy integrating detectors (EIDs) are irradiated with polychromatic X-ray sources, they record a signal proportional to the sum of the energy of every photon, thus the information carried by the energy of individual photons is lost. In energy integrated images, high energy photons weigh more than low energy ones, the latter creating higher contrast between tissues, and Poisson noise from high energy photons is enhanced. Additionally, dark current and noise sources (electronic noise, Swank noise, etc.) are added to the signal (see Section I, Chapter 14 of this book). As a result, EIDs are limited in terms of signal-to-noise ratio (SNR) and dynamic range.
