Basic investigation on reduction of exposure doses in digital subtraction angiography

The present study was designed to determine whether or not exposure doses can be reduced in digital subtraction angiography (DSA) without deteriorating image quality. Incident doses on the acrylic plate were measured when exposing to routine radiation doses in DSA. In this situation, the distance from X-ray tube focus to the image intensifier (II), FID, was defined as 100 cm and irradiation field corresponded to each II. The incident dose increased with increasing the thickness of the subject. It also increased when the size of incident surface was small. Exposure doses in DSA were reduced by approximately 20% when the Graedel method having II 40 cm in diameter was used, although this method would not be anticipated because of the need of II having a larger diameter and complicated procedure of radiographic grid. When the amount of contrast medium was approximately 1.5 times larger than the usual one, exposure doses were reduced by approximately 50% or more in DSA. Considering the recently developed non-ionic contrast medium that is relatively non-invasive, increasing the amount of contrast medium seemed to be the best as a simple method for reducing radiation doses in routine practice. (N.K.)