Describes x-ray spectral imaging detectors based on cadmium zinc telluride (CdZnTe) and cadmium telluride (CdTe) materials; Presents novel computed tomography (CT) and x-ray clinical applications of photon-counting detectors; Considers the future use of CT scanners as both an anatomical and a functional modality in areas typically reserved for nuclear medicine techniques; Addresses pulse pileup, incomplete charge collection, and other phenomena that can degrade the spectral response of photon-counting detectors; Examines silicon photomultipliers used in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) systems