CANCELLATION OF MOTION ARTIFACT IN MRI DUE TO 2D RIGID TRANSLATIONAL MOTION

A new algorithm for cancelling MRI artifact due to translational motio n in the image plane is described. Unlike the conventional iterative p hase retrieval algorithm, in which there is no guarantee for the conve rgence, a direct method for estimating the motion is proposed. In the previous approach, the motions in the readout(x-) direction and the ph ase encoding(y-) direction are estimated simultaneously. However, the feature of the each x- and y-directional motion is different. Based on the analysis of their features, each x- and y-directional motion is c ancelled by different algorithms in two steps. First, we notice that t he x-directional motion corresponds to a shift of the x-directional sp ectrum of the MRI signal, so the x-directional motion can be cancelled by shifting the spectrum in inverse direction. Next, the y-directiona l motion is cancelled using a new constraint, with which the motion co mponent and the true image component can be separated. The algorithm i s shown to be effective by simulations. (C) 1997 Elsevier Science Ltd.