Figure 4
From: Dynamic K-edge Subtraction Fluoroscopy at a Compact Inverse-Compton Synchrotron X-ray Source
Image processing scheme for conventional temporal subtraction and K-edge subtraction (KES) imaging. First, unfiltered and iodine-filtered images are dark current, flatfield and flux corrected. In conventional temporal subtraction, the first unfiltered image is taken as a mask image and logarithmically subtracted from all following unfiltered images to generate the difference images. In KES, two subsequent unfiltered and iodine filtered images are subtracted. For these, two images with energies below and above the iodine K-edge need to be calculated. By weighting the iodine filtered image b, the loss in intensity of the part of the spectrum below the K-edge is corrected for. Subtracting this weighted iodine filtered image d from the unfiltered image a, produces a high energy image e, where only the part of the spectrum above the K-edge contributes to the image. To produce a low energy image, the remaining high energy part of the spectrum in the weighted iodine image d must be eliminated. This can be done by weighting the unfiltered image a such that it fits to the remaining high energy peak in the weighted iodine filtered image d. By subtracting the weighted unfiltered image c from the weighted iodine filtered image d, one obtains the low energy image f. The high and low energy images are then logarithmized and subtracted to obtain the KES image.
