Contrast Enhancement Based on Eigencanceler Beamforming Applied to Medical Ultrasound Imaging

Using adaptive minimum variance beamforming (MV) results in a significant improvement in image resolution, but it’s success in enhancing contrast has not yet been satisfactory. In some researches, eigenspace-based minimum variance beamforming (EIBMV) method has been applied to medical ultrasound imaging system, so that it has improved image contrast while maintaining its resolution. In this paper we apply another eigenspace-based beamforming called eigencanceler (EC) and show it can yield more satisfactory results. However EC needs the noise – interference covariance matrix, whereas the MV and EIBMV use the data covariance matrix. So an altered EC is proposed for the ultrasound imaging. In this method, while canceling the desired signal does not occur, any weight vector is considered to lie in the noise subspace, the subspace orthogonal to the dominant eigenvectors. Otherwise, the weight vector is defined uniformly. Simulation results show the superiority of this method over the MV and EIBMV methods in the contrast aspect. Moreover, the method is more robust against the sound speed errors and can obtain images with better definition of boundaries.