title: Improved in vivo diffusion tensor imaging of human cervical spinal cord.
abstract: We describe a cardiac gated high in-plane resolution axial human cervical spinal cord diffusion tensor imaging (DTI) protocol. Multiple steps were taken to optimize both image acquisition and image processing. The former includes slice-by-slice cardiac triggering and individually tiltable slices. The latter includes (i) iterative 2D retrospective motion correction, (ii) image intensity outlier detection to minimize the influence of physiological noise, (iii) a non-linear DTI estimation procedure incorporating non-negative eigenvalue priors, and (iv) tract-specific region-of-interest (ROI) identification based on an objective geometry reference. Using these strategies in combination, radial diffusivity (λ(⊥)) was reproducibly measured in white matter (WM) tracts (adjusted mean [95% confidence interval]=0.25 [0.22, 0.29] μm(2)/ms), lower than previously reported λ(⊥) values in the in vivo human spinal cord DTI literature. Radial diffusivity and fractional anisotropy (FA) measured in WM varied from rostral to caudal as did mean translational motion, likely reflecting respiratory motion effect. Given the considerable sensitivity of DTI measurements to motion artifact, we believe outlier detection is indispensable in spinal cord diffusion imaging. We also recommend using a mixed-effects model to account for systematic measurement bias depending on cord segment.
authors.affiliation: Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA. jxu@umn.edu
authors.forename: Junqian
authors.initials: J
authors.lastname: Xu
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Shimony
authors.forename: Eric C
authors.initials: EC
authors.lastname: Klawiter
authors.forename: Abraham Z
authors.initials: AZ
authors.lastname: Snyder
authors.forename: Kathryn
authors.initials: K
authors.lastname: Trinkaus
authors.forename: Robert T
authors.initials: RT
authors.lastname: Naismith
authors.forename: Tammie L S
authors.initials: TL
authors.lastname: Benzinger
authors.forename: Anne H
authors.initials: AH
authors.lastname: Cross
authors.forename: Sheng-Kwei
authors.initials: SK
authors.lastname: Song
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000473:pathology*; D000465:Algorithms; D002574:Cervical Vertebrae / Q000033:anatomy & histology; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013116:Spinal Cord / Q000166:cytology*; D055815:Young Adult