Differential radiography by electro-optical means

Differential radiography is arteriography in which electronic and optical methods are employed to display only the difference in information stored on two radiographs. Current practice in arteriography is to compare visually a radiograph made subsequent to the injection of a radiopaque dye with a radiograph taken from the same position but prior to the injection of the dye. The first radiograph contains structural information primarily whereas the second contains structural information plus the circulatory information made visible by the opaque dye. In differential radiography, the two radiographs are viewed and subtracted electronically--only the difference is displayed for the observer.