Intravenous angiography in combination with film subtraction has a limited applicability due to the cumbersome film handling procedure and moreover offers only a limited contrast gain factor. Digital subtraction on the other hand can provide a much larger contrast gain factor so that large-area contrast differences can be visualised much better. Some of the main topics such as contrast gain factor and dynamic range of the two techniques are discussed. Experiments with low contrast phantoms prove that Digital Vascular Imaging (DVI) is superior as regards contrast gain.
"Comparison Of Enhancement Capabilities Of Film Subtraction And Digital Subtraction Methods", Proc. SPIE 0314, Digital Radiography, (4 November 1981); doi: 10.1117/12.933032; https://doi.org/10.1117/12.933032