Energy-resolved Compton scatter estimation for micro-CT

Abstract

X-ray scatter can cause significant distortion in CT imaging especially with the move to cone-beam geometries. Incoherent scatter (Compton scatter) is known to reduce the energy of scattered photons according to the angle of the scattering. The emergence of energy-resolved x-ray detectors offers an opportunity to produce and apply more accurate scatter estimates leading to improved image quality. We have developed a scatter estimation algorithm that accounts for the variation in scatter with incident radiation energy. Where existing methods generate estimates of scatter for the complete detected energy band, our new method produces separate estimates for each of the energy bands that are measured allowing a more focused correction of scatter. Our method is intended to be used in an iterative compensation framework like that of Ruhrnschopf and Klingenbeck (2011); it calculates the scatter contribution to each energy bin used in a scan based on the current volume estimate. Comparisons with Monte Carlo simulations indicate that this algorithm is effective at estimating the scatter level in separate energy bins. We found that the amount of scatter that loses enough energy to hop between energy bands is small enough to neglect but that scatter intensity is dependent on the incident energy so application of a spectrally-aware compensation technique is valuable.