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Convolution-filtering methods and direct beam stop techniques have previously been investigated for estimation of scatter-glare distribution in images acquired using digital fluoroscopic systems. The purpose of this study is to compare the error in scatter-glare estimation for a direct beam stop technique and a convolution technique. Also, the change in scatter-glare intensity due to contrast material injection for ventriculography and coronary arteriography was quantified. Three different methods were used to estimate scatter-glare intensity in humanoid chest phantom and animal model images. A lead strip was used to scan the x-ray field for direct measurement of scatter-glare intensity in every pixel in the image. An array of lead beam-stops were used in order to sample scatter-glare intensity. An interpolation technique was used to estimate scatter-glare intensity for the remaining pixels in the image. Scatter-glare intensity was also estimated using a convolution filtering technique. This technique utilizes exposure parameters and image gray levels to assign equivalent Lucite thicknesses for every pixel in the image. The thickness information is then used to estimate scatter-glare intensity on a pixel-by-pixel basis. Finally, an array of lead beam-stops were used to measure the change in scatter-glare intensity due to contrast material injection. This was done by leaving the array of lead beam-stops in the x-ray beam for ventriculography and coronary arteriography procedures. The results indicate that the array of lead beam-stops produces significant errors in estimating scatter-glare intensity. This is primarily due to the fact that contrast material injection significantly changes scatter-glare intensity. The scatter- glare intensity was changed by up to 19% and 88% during coronary arteriography and ventriculography, respectively. In conclusion, contrast material injection significantly changes the scatter-glare intensity during coronary arteriography and ventriculography procedures. Therefore, convolution-filtering techniques are more suited for cardiac imaging, where scatter- glare intensity significantly changes during image acquisition.
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