The development and use of digital subtraction angiography

Abstract

The technique of radiographic subtraction was first described in 1935 (Ziedses des Plantes, 1935), although the first English language paper on the subject did not appear until 27 years later (Hanafee & Stout, 1962). This commented that the technique provided an economical photographic method of reducing the confusion of overlapping bony structures in angiographic studies. The advantages of radiographic subtraction can be summarized as (a) providing image enhancement and (b) improving and bringing out detail in areas hidden by overlying bone or poor contrast. These features may therefore save the situation when the density of contrast medium is insufficient to show a lesion (Leeds, 1974). Previously, intravenous injections of contrast medium had been used to show the aorta and other arteries (Steinberg et al, 1959).Digitization of images was introduced experimentally (Meyers et al, 1963), with the aim of automating the reading of radiographs. Manipulation of digitized information became widely used when computerized tomographic (CT) scanners were introduced, and an early use of computerized subtraction was for the assessment of regional cerebral blood flow (Zilkha et al, 1976) in which pre-injection scans were subtracted from postinjection scans to allow analysis of areas of the scan sections. A series of papers then appeared from workers at the University of Wisconsin describing “computerized fluorography” in which images from an image intensifier were collected, amplified logarithmically and digitized, before being integrated, processed and redisplayed on a monitor (Kruger et al, 1979).