1. A multi-energy computed tomography (CT) imaging system comprising: an energy-discriminating, photon-counting X-ray detector, comprising a plurality of detector cells each providing measurements corresponding to at least two energy bins and being configured to produce projection data in response to X-ray photons that reach the X-ray detector and to produce an electrical signal comprising a recorded count for each of the at least two energy bins recorded during a data acquisition time period and a total energy intensity recorded during the data acquisition time period; and data processing circuitry configured to receive the electrical signal from one or more of the plurality of detector cells, to generate a simulated count rate for each of the at least two energy bins by using the total energy intensity in a detector pile-up model, to determine a set of energy intensity dependent material decomposition vectors, and, for each projection data measured by the one or more detector cells, to perform material decomposition by utilizing the measured count during a data acquisition time period for each of the at least two energy bins and a material decomposition vector selected from the set of energy intensity dependent material decomposition vectors and corresponding to the measured total energy intensity for the one or more of the plurality of detector cells.