Compensation for scattered radiation in dual-energy imaging using partially transparent shields

In this paper we present a method for the compensation for scattered radiation in dual-energy imaging. The method uses shields (PTS), partially transparent for x-radiation, positioned between the x-ray source and the detector. By comparing the detected signals under and beside the shields, and using data from the dual-energy calibration procedure with basis materials, the radiation scatter can be calculated at the location of the shields. In a first implementation of the technique many shields are positioned at regular distances in the imaging field. The radiation scatter in the entire image can then be calculated by interpolation techniques. A second implementation of the technique makes use of a robust convolution with a low-pass filter. The parameters of the convolution kernel are determined by PTS-measurements at a limited amount of well-chosen locations of the object. After substraction of the radiation scatter, the images can be compensated for the effect of the shields. We tested the method with images of an artificial polystyrene phantom and with humanoid chest images, made with a computed radiography system.