A multiscale and multi-orientation contrast enhancement method for digital mammography

A multidirectional and multiscale contrast enhancement method for digital mammography images is proposed. The main idea is to enhance selectively the contrast of the sub-bands according to their position and orientation in the frequency domain. The image is then decomposed into different scales and orientations using the steerable pyramid transform. The contrast in each selected band is enhanced with a nonlinear mapping function. The enhanced image is then obtained by a pyramid reconstruction of these contrasted bands. This results in a significant improvement of the mammography features visibility. To evaluate the quality of the enhanced images, a new objective quality measure based on the spectral energy analysis is used.