Spectral x-ray imaging using a photon counting x-ray detector (PCXD) transmits a broad spectrum x-ray beam through an object, detects the transmitted x-ray beam with the PCXD and processes the detected signals to determine material characteristics of the object using both the detected signals as a function of detector layer and the detected signals as a function of the particular energy band. Each detector layer of the multiple detector layers produces at least two signals, each signal representing a detected x-ray intensity in a particular energy band, and the depth information contained in the separate read-out channels.
