Contrast enhancement by dyadic wavelet analysis

Introduces a method for accomplishing mammographic feature analysis by multiresolution representations of the dyadic wavelet transform. The authors´ approach consists of the application of nonlinear enhancing functions within levels of a multiresolution representation. They show that there exists a simple constraint for functions such that image enhancement is guaranteed. Furthermore, a simple case in which the enhancement operator is a constant multiplier is mathematically equivalent to traditional unsharp masking. The authors show quantitatively that transform coefficients, modified within each level by nonlinear operators, can make more obvious unseen or barely seen features of mammography without requiring additional radiation. The authors´ results are compared with traditional image enhancement techniques by measuring the local contrast of known mammographic features