A versatile wavelet domain noise filtration technique for medical imaging.pdf

SUBMITTED FOR PUBLICATION TO: IEEE TRANS. ON MEDICAL IMAGING, JUNE 28, 2002 1 A Versatile Wavelet Domain Noise Filtration Technique for Medical Imaging Aleksandra Pizurica, Wilfried Philips, Ignace Lemahieu, and Marc Acheroy Abstract In this paper, we propose a robust wavelet domain method for noise filtering in medical images. The proposed method adapts itself to various types of image noise as well as to the preference of the medical expert: a single parameter can be used to balance the preservation of (expert-dependent) relevant details against the degree of noise reduction. The algorithm exploits generally valid knowledge about the correlation of significant image features across the resolution scales to perform a preliminary coefficient classification. This preliminary coefficient classification is used to empirically estimate the statistical distributions of the coefficients that represent useful image features on the one hand and mainly noise on the other. The adaptation to the spatial context in the image is achieved by using a wavelet domain indicator of the local spatial activity. The proposed method is of low-complexity, both in its implementation and execution time. The results demonstrate its usefulness for noise suppression in medical ultrasound and magnetic resonance imaging. In these applications, the proposed method clearly outperforms single-resolution spatially adaptive algorithms, in terms of quantitative performance measures as well as in terms of visual quality of the images. I. Introduction In medical images, noise suppression is a particularly delicate and difficult task. A trade off between noise reduction and the preservation of actual image features has to be made in a way that enhances the diagnostically relevant image content. Image processing specialists usually lack the biomedical expertise to judge the diagnostic relevance of the denoising results. For example, in A. Pizurica? and W. Philips are with the Department for Telecommunicati