Scatter-glare estimation for digital radiographic systems: Comparison of digital filtration and sampling techniques

The scatter and veiling glare distribution in images acquired with a digita l subtraction angiography imaging system was estimated using a digital filt ration and a beam-stop technique. The digital filtration technique utilizes exposure parameters and image gray levels to estimate scatter-glare intens ity based on previous phantom measurements. The beam-stop technique uses an array of lead discs in order to sample scatter-glare intensity for each pa tient. To test the ability of digital filtration and beam-stop techniques t o estimate the scatter-glare intensity, they were applied to images of post mortem swine animal models at different projections and beam energies. The systematic and root-mean-square (rms) percentage errors of these estimates were obtained by comparison to directly measured scatter-glare images using a scanning lead strip technique. The average rms percentage error for the digital filtration and beam-stop techniques were 8.07% and 6.67%, respectiv ely. The changes in scatter-glare intensity due to contrast injection durin g coronary arteriography and ventriculography were also measured using the beam-stop technique. The maximum changes in scatter-glare intensities durin g coronary arteriography and ventriculography were 19 and 88%, respectively . The results indicate that the digital filtration technique is more suited for applications such as coronary arteriography and ventriculography where ! the iodinated contrast material significantly changes the scatter-glare i ntensity.