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Tracking discrete off‐resonance markers with three spokes (trackDOTS) for compensation of head motion and B 0 perturbations: Accuracy and performance in anatomical imaging
Author(s) -
Jorge João,
Gretsch Frédéric,
Gallichan Daniel,
Marques José P.
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26654
Subject(s) - magnetic resonance imaging , computer science , artificial intelligence , computer vision , nuclear magnetic resonance , match moving , tracking (education) , motion (physics) , head (geology) , image quality , physics , scanner , motion compensation , nuclear medicine , medicine , radiology , geology , psychology , pedagogy , geomorphology , image (mathematics)
Purpose To develop a novel approach for head motion and B 0 field monitoring based on tracking discrete off‐resonance markers with three spokes (trackDOTS). Methods Small markers filled with acetic acid were built and attached to a head cap. Marker positions and phase were tracked with fast MR navigators (DotNavs) consisting of three off‐resonance, double‐echo, orthogonal one‐dimensional projections. Individual marker signals were extracted using optimized coil combinations, and used to estimate head motion and field perturbations. To evaluate the approach, DotNavs were integrated in submillimeter MP2RAGE and long–echo time gradient‐echo sequences at 7 Tesla, and tested on six healthy volunteers. Results The DotNav‐based motion estimates differed by less than 0.11 ± 0.09 mm and 0.19 ± 0.17 ° from reference estimates obtained with an existing navigator approach (FatNavs). Retrospective motion correction brought clear improvements to MP2RAGE image quality, even in cases with submillimeter involuntary motion. The DotNav‐based field estimates could track deep breathing–induced oscillations, and in cases with small head motion, field correction visibly improved the gradient‐echo data quality. Conversely, field estimates were less robust when strong motion was present. Conclusions The trackDOTS approach is suitable for head‐motion tracking and correction, with significant benefits for high‐spatial‐resolution MRI. With small head motion, DotNav‐based field estimates also allow correcting for deep‐breathing artifacts in T 2 *–weighted acquisitions. Magn Reson Med 79:160–171, 2018. © 2017 International Society for Magnetic Resonance in Medicine.