X-ray projection imaging, introduced in the early 20^th century, was for a long time the only and still is a major routine diagnostic procedure that can be performed on the intact human body. With the advent of Computed Tomography in 1973, for the first time, a true 3D imaging of anatomical structures became feasible. Besides, digital recording and processing allowed further developments such as subtraction angiography in real-time or direct x-ray imaging without wet photographic methods.