Convolution Filtering Technique For Estimating Scatter Distributions In Radiographic Images
Lane Alan Love, Robert A. Kruger, Margaret A. Simons · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1986
The degree to which beam hardening due to iodine, and x-ray and light scatter within the imaging chain, cause a nonlinear videodensitometric response of DSA grey level to iodine areal density were studied. Beam hardening effects were found to be secondary to the effects of scatter. Local scatter estimates could reliably be made, using an array of small lead beam-stops, which provided estimates of the scatter contribution regionally within an image. When the local scatter levels were subtracted from component images prior to DSA logarithmic subtraction, the DSA grey-scale response was made approximately linear with iodine areal density. Convolution filtering was studied as a method for estimating the scatter over an entire image based on beam-stop measurements made at a few points within the image. Simple, large-size (.0100x100 pixels) convolution kernels were capable of reproducing the scatter distribution within a chest image with an rms percentage error of <10% over a 36 cm field of view. The method should be implementable using a single lead beam-stop placed over a highly transmissive region in a patient.