An autofocus algorithm for the automatic correction of motion artifacts in MR images

We present the use of an entropy focus criterion to enable automatic focussing of motion corrupted magnetic resonance images. Our technique can determine unknown patient motion or use knowledge of motion from other measures as a starting estimate. The motion estimate is used to compensate the acquired data and is iteratively refined using the image entropy. Our entropy criterion focuses the whole, image principally by favoring the removal of motion induced ghosts and blurring from otherwise dark regions of the image. Using only the image data, and no special hardware or pulse sequences, we demonstrate correction for arbitrary rigid-body translational motion in the imaging plane and for a single rotation. Extension to 3D and more general motion should be possible.