A spectral calibration technique for x-ray CT

Spectral reconstruction algorithms for x-ray CT require an accurate spectral model of the system, including the spectrum of the photons emitted by the source and the spectral sensitivity of the detector. Although these components of the spectral model have been characterized in previous studies, there might be additional components that are unaccounted for, such as the inherent filtration of the x-ray source and the detector. In this study, we present a technique for measuring the inaccuracies in the spectral model and accounting for them. This technique entails the acquisition of photon measurements with several materials placed between the source and the detector, and the solution of a linear system of equations. We test the accuracy of this technique in simulations, and demonstrate its potential to improve the results of spectral reconstruction.