Digital subtraction angiography

Digital subtraction angiography (DSA) is a fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a "pre-contrast image", or mask, from subsequent images once the contrast medium has been introduced into a structure (hence the term "digital subtraction angiography"). Subtraction angiography was first described in 1935, and in 1962, it was described in English sources as a manual technique. Digital technology made DSA practical starting in the 1970s.