Automatic compensation of motion artifacts in MRI

Patient motion during the acquisition of a magnetic resonance image can cau se blurring and ghosting artifacts in the image. This paper presents a new post-processing strategy that can reduce artifacts due to in-plane, rigid-b ody motion in times comparable to that required to re-scan a patient. The a lgorithm iteratively determines unknown patient motion such that correction s for this motion provide the best image quality, as measured by an entropy -related focus criterion. The new optimization strategy features a multi-re solution approach in the phase-encode direction, separate successive one-di mensional searches for rotations and translations, and a novel method requi ring only one re-gridding calculation for each rotation angle considered, A pplicability to general rigid-body in-plane rotational and translational mo tion and to a range of differently weighted images and k-space trajectories is demonstrated. Motion artifact reduction is observed for data from a pha ntom, volunteers, and patients. Magn Reson Med 41:163-170, 1999. (C) 1999 W iley-Liss, Inc.