title: Improved reduction of motion artifacts in diffusion imaging using navigator echoes and velocity compensation.
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.
authors.affiliation: NMR Research Unit, Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, United Kingdom.
authors.forename: C A
authors.initials: CA
authors.lastname: Clark
authors.forename: G J
authors.initials: GJ
authors.lastname: Barker
authors.forename: P S
authors.initials: PS
authors.lastname: Tofts
mesh_terms: D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009038:Motion