Systems and methods for k-edge-based x-ray imaging having improved contrast-to-noise ratio

An X-ray imaging system, comprising:

• an X-ray source configured to direct a beam of X-ray radiation at an object;
• an energy-discriminating radiation detector comprising a plurality of radiation sensors configured to detect X-rays from the X-ray source that have been attenuated by the object;
• and
• detector read-out circuitry configured to determine an energy of X-ray photons detected by the plurality of radiation sensors and to generate photon count data by counting a number of detected photons in a plurality of energy bins, the plurality of energy bins comprising a first energy bin having a maximum energy threshold that is less than a K-edge energy of a material of interest, and a second energy bin having a minimum energy threshold that is greater than the K-edge energy of the material of interest;
• and
• a processor configured to generate an X-ray image of the object using the photon count data, wherein photons detected by the plurality of radiation sensors that are determined to have an energy within a gap region between the maximum energy threshold of the first energy bin and the minimum energy threshold of the second energy bin are not included in the photon count data used to generate the X-ray image of the object.