X ray image subtraction by digital means

A conventional method of removing unwanted background information from radiographic images is to use photographic techniques. An alternative approach is the digital processing of x ray difference images. This approach offers the advantage over photographic methods in that it permits the performance of nonlinear operations, such as compensation for film characteristics, thus offering greater flexibility in the presentation of x ray images and greater reliability in their interpretation. This paper describes the features and implementation of a new digital approach and presents experimental results obtained from processing two sets of angiograms.