Steerable pyramid for contrast enhancement and directional structures detection

The object of this work is the application of steerable filters for the diagnosis of breast cancer. Because of the very specific geometry of malignant densities, we intend to apply a multiscale and orientation shiftable method for the detection of breast cancer in mammograms. Stellate masses have an irregular appearance and are frequently surrounded by a radiating pattern of linear spicules. Multiscale approaches using oriented filters have proved to be efficient to detect such stellate patterns. We first use the fact that tumors are always brighter than the surrounding tissues to locate suspicious regions. The detection is then based on steerable filters, which can be steered to any orientation fixed by the user, and are synthesized using a limited number of basis filters. These filters are used in a recursive multi-scale transform: the steerable pyramid. Using the steerable pyramid, oriented contrast enhancement is performed. The resulting enhanced image is then analyzed to estimate whether a stellate mass is present or not.