X-ray medical image processing using directional wavelet transform

Multi-resolution and multi-orientation are part of the biological mechanism of human visual system. The interest in multi-resolution image analysis has been growing rapidly. Comparatively, however, the multi-orientation method has received less attention. Based on the relationship between multifrequency channel decomposition and the wavelet model developed by Mallat [1989], a combined multiresolution/multi-orientation representation by directional wavelet transform (DWT) is introduced in this paper. Because of its high orientation selectivity, the DWT allows the processing of directional information more efficiently. It is applied successfully to feature enhancement and extraction of X-ray mammographic images