Digital subtraction angiography--a critical analysis.

The advantages and disadvantages claimed for intravenous and intra-arterial digital subtraction angiography (DSA) are critically examined. The parameters determining image quality and the factors degrading the image in intravenous DSA are discussed. It is argued that many of the patients specifically referred for intravenous digital subtraction studies are unsuitable for this examination either because poor image quality is to be expected and/or because the large contrast load inherent in this type of examination is undesirable.