Scatter considerations in ultra-high-resolution high-energy X-ray transmission imaging systems

The existence of Compton scatter will lower the performance of radiation imaging systems. Scatter considerations in high-energy X-ray imaging systems are different from low-energy ones. We have developed a method for analytically calculating scatter point spread function (PSF) in ultra-high-resolution, high-energy (UHR-HE) X-ray transmission systems with parallel slat collimator, and applied it to several typical dense objects: a homogeneously attenuating medium, a straight-edge object, and a more practical axisymmetric model (a circular cylindrical object). The scatter distribution along the detector plane can be theoretically calculated by integrating scatter PSF over the full-width of collimator scatter response function. Our method is compared with Monte Carlo simulation for a straight-edge object, and the results fit well. In UHR-HE CT systems, projection error due to scatter is step-like near the sharp edge, and it may evoke high-frequency artifacts in the final reconstruction image, and consequently decreases the system dectectability of high-contrast, microdefects in industrial applications.