Physics-based Modeling of Energy Threshold Induced Spectral Inconsistency and Its Adaptive Correction Scheme for photon-counting CT

The spectral inconsistency across detector pixels is still a major challenge that could directly lead to obvious artifacts in reconstructed CT images and severe inaccuracies in material discrimination. This work attempts to develop a novel approach of modeling the energy threshold induced spectral inconsistency for photon-counting CT (PCCT) to adaptively characterize and correct for spectral effects. This proposed method is based on the general model expression of photon counts, adds variables to the integration term to represent spectral distortion and furthermore takes a threshold-related nonuniformity bias factor into account at integration bounds. In this work, we assume that the variables associated with spectral distortion are mainly related to the system geometry and the detector material, there is only threshold-related nonuniformity bias factor to change with the energy-threshold, regardless of some nonideal effects like pileup and charge sharing. After simplification, we solve the linear equations to get the threshold-related nonuniformity bias at different thresholds, and the corrected photon counts can be calculated together with the spectral distortion variables have been worked out at the first reference threshold. Experimental results showed that the ring and band artifacts caused by spectral inconsistency were significantly reduced, the quality of reconstructed images is visibly improve. And the universality and robustness of our method are also demonstrated preliminary.