Patent ID: 8422636

Claim:
An imaging system comprising: an x-ray source that emits a beam of x-rays toward an object to be imaged; a detector that receives x-rays emitted from the x-ray source; a data acquisition system (DAS) operably coupled to the detector, the DAS configured to count photon hits in the detector that occur at photon energies above at least a low keV threshold, a medium keV threshold, and a high keV threshold; and a computer operably coupled to the DAS and programmed to: vary each of the medium keV threshold and the high keV threshold over a continuous keV range during data acquisition to define low, medium, and high keV bins that are based on the low, medium, and high keV thresholds; obtain photon counts in the low, medium, and high keV bins in a plurality of keV threshold combinations; calculate a noise variance as a function of at least one of the keV thresholds; and identify a noise minimum and low, medium, and high keV thresholds that correspond thereto.