ABSTRACT
Projection radiography and computed tomography (CT) have been gold standards for screening, diagnostic, and therapeutic medical imaging in the last several decades [1-4]. Radiography and CT systems employ polyenergetic X-ray beams with broad energy spectra generated by conventional X-ray tubes. Until now, these systems use radiation detectors based on the energy integration principle, that is, X-ray photons (usually several thousand photons per pixel) are absorbed and energies of all photons summed up to provide a single analog signal. On the other hand, X-ray photons are inherently discrete, and it would be straightforward to detect (count) each photon separately during image acquisition. Such a photon-counting mode would allow for rejecting electronics noise by setting an appropriate energy threshold for the detector electronics. In addition, the photon-counting detector would allow for measuring the energy of each X-ray photon. Energy-selective data acquisition, in turn, would enable material-selective imaging for major clinical applications.
