Improved reduction of motion artifacts in diffusion imaging using navigator echoes and velocity compensation |
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Authors: | Clark C A Barker G J Tofts P S |
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Affiliation: | NMR Research Unit, Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, United Kingdom. |
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Abstract: | Navigator echoes provide a means with which to remove motion artifacts from diffusion-weighted images obtained using any multishot imaging technique. However, residual motion artifact is often present in the corrected images rendering the technique unreliable. It is shown that velocity-compensated diffusion sensitization when used in tandem with a navigator echo further reduces the degree of residual motion artifacts present in the corrected images and improves the reliability and clinical utility of the technique. This is demonstrated by applying a method for quantification of motion artifact to brain images of healthy volunteers scanned using both conventional (Stejskal-Tanner) and velocity-compensated gradient sensitization. Other factors affecting the efficacy of the navigator echo technique, such as brain pulsatile motion, gradient b factor, and navigator echo signal-to-noise ratio, are also discussed. |
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Keywords: | diffusion motion artifacts navigator echoes MRI |
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