Scatter correction algorithm for digitally acquired radiographs: theory and results.

A scatter correction algorithm for digitally acquired radiographs (SCADAR) is presented. SCADAR requires the acquisition of two digital images, taken at different object-to-detector distances. These two images are digitally magnification compensated, and subtracted. The primary component in the resulting difference image delta is mathematically eliminated, and hence the delta image is used as a measure of the local contribution of scattered radiation. A gray scale transformation is used to transform the delta image to a scattered component image, which is then smoothed by Fourier filtering, using a matched filter to increase the signal-to-noise ratio. The smoothed scatter image is then subtracted from its corresponding original image, resulting in the corrected SCADAR image. Implementation of SCADAR can result in a large increase in image contrast, and a significant reduction in shading due to scattered radiation effects. The mathematical derivation of the algorithm is developed, and experimental verification is given for some of the principles used. Using experimental images acquired from scattering phantoms, the results of SCADAR on various image parameters such as contrast and detail signal-to-noise ratio are discussed.