This invention relates to a method for de-noising digital radiographic
images based upon a wavelet-domain Hidden Markov Tree (HMT) model. The
method uses the Anscombe's transformation to adjust the original image to
a Gaussian noise model. The image is then decomposed in different
sub-bands of frequency and orientation responses using a dual-tree
complex wavelet transform, and the HMT is used to model the marginal
distribution of the wavelet coefficients. Two different methods were used
to denoise the wavelet coefficients. Finally, the modified wavelet
coefficients are transformed back into the original domain to get the
de-noised image.