title: Retrospective intra-scan motion correction.
abstract: This paper analyzes the effects of intra-scan motion and demonstrates the possibility of correcting them directly in k-space with a new automatic retrospective method. The method is presented for series of 2D acquisitions with Cartesian sampling. Using a reference k-space acquisition (corrected for translations) within the series, intra-scan motion parameters are accurately estimated for each trajectory in k-space of each data set in the series resulting in pseudo-random sample positions. The images are reconstructed with a Bayesian estimator that can handle sparse arbitrary sampling in k-space and reduces intra-scan rotation artefacts to the noise level. The method has been assessed by means of a Monte Carlo study on axial brain images for different signal-to-noise ratios. The accuracy of motion estimates is better than 0.1 degrees for rotation, and 0.1 and 0.05 pixel, respectively, for translation along the read and phase directions for signal-to-noise ratios higher than 6 of the signals on each trajectory. An example of reconstruction from experimental data corrupted by head motion is also given.
authors.affiliation: Laboratoire de RMN, CNRS UMR 5012, Université Claude Bernard LYON I, CPE, Domaine scientifique de la Doua, 3 rue Victor Grignard, F-69616 Villeurbanne, France.
authors.forename: Marc E
authors.initials: ME
authors.lastname: Bourgeois
authors.forename: Frank T A W
authors.initials: FT
authors.lastname: Wajer
authors.forename: Muriel
authors.initials: M
authors.lastname: Roth
authors.forename: André
authors.initials: A
authors.lastname: Briguet
authors.forename: Michel
authors.initials: M
authors.lastname: Décorps
authors.forename: Dirk
authors.initials: D
authors.lastname: van Ormondt
authors.forename: Christoph
authors.initials: C
authors.lastname: Segebarth
authors.forename: Danielle
authors.initials: D
authors.lastname: Graveron-Demilly
mesh_terms: D000465:Algorithms; D000818:Animals; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological; D015233:Models, Statistical; D009038:Motion; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity