title: Cervical Spinal Cord DTI Is Improved by Reduced FOV with Specific Balance between the Number of Diffusion Gradient Directions and Averages.
abstract: OBJECTIVE
  Reduced-FOV DTI is promising for exploring the cervical spinal cord, but the optimal set of parameters needs to be clarified. We hypothesized that the number of excitations should be favored over the number of diffusion gradient directions regarding the strong orientation of the cord in a single rostrocaudal axis.
  
  
  METHODS
  Fifteen healthy individuals underwent cervical spinal cord MR imaging at 3T, including an anatomic 3D-Multi-Echo Recombined Gradient Echo, high-resolution full-FOV DTI with a NEX of 3 and 20 diffusion gradient directions and 5 sets of reduced-FOV DTIs differently balanced in terms of NEX/number of diffusion gradient directions: (NEX/number of diffusion gradient directions = 3/20, 5/16, 7/12, 9/9, and 12/6). Each DTI sequence lasted 4 minutes 30 seconds, an acceptable duration, to cover C1-C4 in the axial plane. Fractional anisotropy maps and tractograms were reconstructed. Qualitatively, 2 radiologists rated the DTI sets blinded to the sequence. Quantitatively, we compared distortions, SNR, variance of fractional anisotropy values, and numbers of detected fibers.
  
  
  RESULTS
  Qualitatively, reduced-FOV DTI sequences with a NEX of ≥5 were significantly better rated than the full-FOV DTI and the reduced-FOV DTI with low NEX (N = 3) and a high number of diffusion gradient directions (D = 20). Quantitatively, the best trade-off was reached by the reduced-FOV DTI with a NEX of 9 and 9 diffusion gradient directions, which provided significantly fewer artifacts, higher SNR on trace atb= 750 s/mm2and an increased number of fibers tracked while maintaining similar fractional anisotropy values and dispersion.
  
  
  CONCLUSIONS
  Optimized reduced-FOV DTI improves spinal cord imaging. The best compromise was obtained with a NEX of 9 and 9 diffusion gradient directions, which emphasizes the need for increasing the NEX at the expense of the number of diffusion gradient directions for spinal cord DTI contrary to brain DTI.
authors.affiliation: From the Centre Hospitalier Universitaire de Bordeaux (A.C., V.D., T.T.), Service de NeuroImagerie Diagnostique de Thérapeutique, Bordeaux, France amandine.crombe@ens-lyon.fr.|Institut National de la Santé et de la Recherche Médicale U1215 (A.C., V.D., T.T.), Physiopathologie de la Plasticité Neuronale, Bordeaux, France.|Institut de Bio-Imagerie de Bordeaux (A.C., N.A., B.H., V.D., T.T.), Université de Bordeaux, Bordeaux, France.
authors.forename: A
authors.identifier: http://orcid.org/0000-0003-0098-6482
authors.initials: A
authors.lastname: Crombe
authors.affiliation: Institut de Bio-Imagerie de Bordeaux (A.C., N.A., B.H., V.D., T.T.), Université de Bordeaux, Bordeaux, France.|Centre de Résonance Magnétique des Systèmes Biologiques (N.A., B.H.), Centre National de la Recherche Scientifique Unité Mixte de Recherche 5536, Bordeaux, France.
authors.forename: N
authors.identifier: http://orcid.org/0000-0003-2150-1405
authors.initials: N
authors.lastname: Alberti
authors.affiliation: Institut de Bio-Imagerie de Bordeaux (A.C., N.A., B.H., V.D., T.T.), Université de Bordeaux, Bordeaux, France.|Centre de Résonance Magnétique des Systèmes Biologiques (N.A., B.H.), Centre National de la Recherche Scientifique Unité Mixte de Recherche 5536, Bordeaux, France.|Institut de Neurosciences Cognitives et Intégratives d'Aquitaine (B.H.), Centre National de la Recherche Scientifique Unité Mixte de Recherche 5287, Bordeaux, France.
authors.forename: B
authors.identifier: http://orcid.org/0000-0002-5436-3742
authors.initials: B
authors.lastname: Hiba
authors.affiliation: GE Healthcare (M.U.), Vélizy-Villacoublay, France.
authors.forename: M
authors.identifier: http://orcid.org/0000-0003-4267-5623
authors.initials: M
authors.lastname: Uettwiller
authors.affiliation: From the Centre Hospitalier Universitaire de Bordeaux (A.C., V.D., T.T.), Service de NeuroImagerie Diagnostique de Thérapeutique, Bordeaux, France.|Institut National de la Santé et de la Recherche Médicale U1215 (A.C., V.D., T.T.), Physiopathologie de la Plasticité Neuronale, Bordeaux, France.|Institut de Bio-Imagerie de Bordeaux (A.C., N.A., B.H., V.D., T.T.), Université de Bordeaux, Bordeaux, France.
authors.forename: V
authors.identifier: http://orcid.org/0000-0003-0427-3236
authors.initials: V
authors.lastname: Dousset
authors.affiliation: From the Centre Hospitalier Universitaire de Bordeaux (A.C., V.D., T.T.), Service de NeuroImagerie Diagnostique de Thérapeutique, Bordeaux, France.|Institut National de la Santé et de la Recherche Médicale U1215 (A.C., V.D., T.T.), Physiopathologie de la Plasticité Neuronale, Bordeaux, France.|Institut de Bio-Imagerie de Bordeaux (A.C., N.A., B.H., V.D., T.T.), Université de Bordeaux, Bordeaux, France.
authors.forename: T
authors.identifier: http://orcid.org/0000-0002-7151-6325
authors.initials: T
authors.lastname: Tourdias