Direct scatter distribution measurements. Comparison to Monte Carlo simulations

'Direct' measurement of the scatter point spread function (PSF) was obtained with a digital imaging system for the purpose of comparison of a Monte Carlo (MC) scatter distribution algorithm that takes into account polychromatic spectra and detector absorption characteristics. An image intensifier (II) TV system was used to experimentally acquire digital x-ray scatter images in a geometry designed to eliminate detection of the primary beam and to optimize the dynamic range for scattered radiation as well as correct for image variations caused by veiling glare and shading. Both computer generated and experimentally acquired scatter data were measured in concentric annular bins and individually integrated to provide a direct PSF profile. Results indicate a good match between the MC and experimental PSF's for homogeneous scatter distributions at short range airgaps and radial distances. Discrepancies at larger radial distances are likely due to the spherical II input phosphor geometry. For an II/TV system detector, therefore, geometric image warping correction for pincushion distortion is indicated, as well as modifications in the MC algorithm for geometry of the detector. This will help to minimize differences between simulated and measured system characteristics.