Improvement of image quality in digital subtraction angiography via a variable filter diaphragm

The authors examine by means of comparative series in 25 patients whether and to what extent a special combination of filter diaphragms can improve imaging in digital subtraction angiography. It was found that the filter diaphragm combination should be applied as a matter of principle in case of large absorption differences in the examined region, since this will safely eliminate saturation effects causing artifacts, or partial image losses which are otherwise likely to occur. However, no essential advantages are obtained if the X-ray image is largerly homogeneous. (orig.)