AUTOMATIC CORRECTION OF MOTION ARTIFACTS IN MAGNETIC-RESONANCE IMAGESUSING AN ENTROPY FOCUS CRITERION

We present the use of an entropy focus criterion to enable automatic f ocusing of motion corrupted magnetic resonance images. We demonstrate the principle using illustrative examples from cooperative volunteers. Our technique can determine unknown patient motion or use knowledge o f motion from other measures as a starting estimate, The motion estima te is used to compensate the acquired data and is iteratively refined using the image entropy, Entropy focuses the whole image principally b y favoring the removal of motion induced ghosts and blurring from othe rwise dark regions of the image, Using only the image data, and no spe cial hardware or pulse sequences, we demonstrate correction for arbitr ary rigid-body translational motion in the imaging plane and for a sin gle rotation, Extension to three-dimensional (3-D) and more general mo tion should be possible, The algorithm is able to determine volunteer motion well. The mean absolute deviation between algorithm and navigat or-echo-determined motion is comparable to the displacement step size used in the algorithm, Local deviations from the recorded motion or na vigator-determined motion are explained and we indicate how enhanced f ocus criteria may be derived, In all cases we were able to compensate images for patient motion, reducing blurring and ghosting.