A diaphragmatic compensating filter for hepatic angiography.

To enhance the clarity of angiographic images, a diaphragmatic compensating filter (DCF) covering the sub-phrenic portion was constructed. The required shape of a DCF for a high optical density part of the angiograms was determined by the distribution limit of the outline of the diaphragms, but the shape of the low optical density part could not be specified. The smallest tolerance of a DCF for the respiratory motion of a diaphragm was 13.2 mm at the film. Thus, a DCF was effective in more than 95.8% of angiograms. Our clinical results showed remarkable improvement in those images. The clinical areas between radiographic images with and without a DCF were improved by more than 27% according to an image analysis system. Therefore a DCF is indispensable in conventional hepatic angiography and digital subtraction angiography. In addition, only one type of a DCF is possible for use in combination with lateral compensating filters.