A DIGITAL FILTRATION TECHNIQUE FOR SCATTER-GLARE CORRECTION BASED ON THICKNESS ESTIMATION

In order to quantitate anatomical and physiological parameters such as vessel dimensions and volumetric blood dow, it is necessary to make c orrections for scatter and veiling glare, which are the major sources of nonlinearities in videodensitometric digital subtraction angiograph y (DSA), A convolution filtering technique has been investigated to es timate scatter-glare distribution in DSA images without the need to sa mple the scatter-glare intensity for each patient, This technique util izes exposure parameters and image gray levels to assign equivalent Lu cite thickness for every pixel in the image, The thickness information is then used to estimate scatter-glare intensity on a pixel-by-pixel basis, To test its ability to estimate scatter-glare intensity, the co rrection technique was applied to images of a Lucite step phantom, ant hropomorphic chest phantom, head phantom, and animal models at differe nt thicknesses, projections, and beam energies, The root-mean-square ( rms) percentage error of these estimates was obtained by comparison wi th direct scatter-glare measurements made behind a lead strip, The ave rage rms percentage errors in the scatter glare estimate for the 25 ph antom studies and the 17 animal studies were 6.44% and 7.96%, respecti vely, These results indicate that the scatter-glare intensity can be e stimated with adequate accuracy for a wide range of thicknesses, proje ctions, and beam energies using exposure parameters and gray level inf ormation.