title: The effect of diffusion gradient direction number on corticospinal tractography in the human brain: an along-tract analysis.
abstract: OBJECTIVE
  We evaluated diffusion imaging measures of the corticospinal tract obtained with a probabilistic tractography algorithm applied to data of two acquisition protocols based on different numbers of diffusion gradient directions (NDGDs).
  
  
  METHODS
  The corticospinal tracts (CST) of 18 healthy subjects were delineated using 22 and 66-NDGD data. An along-tract analysis of diffusion metrics was performed to detect possible local differences due to NDGD.
  
  
  RESULTS
  FA values at 22-NDGD showed an increase along the central portion of the CST. The mean of partial volume fraction of the orientation of the second fiber (f2) was higher at 66-NDGD bilaterally, because for 66-NDGD data the algorithm more readily detects dominant fiber directions beyond the first, thus the increase in FA at 22-NDGD is due to a substantially reduced detection of crossing fiber volume. However, the good spatial correlation between the tracts drawn at 22 and 66 NDGD shows that the extent of the tract can be successfully defined even at lower NDGD.
  
  
  CONCLUSIONS
  Given the spatial tract localization obtained even at 22-NDGD, local analysis of CST can be performed using a NDGD compatible with clinical protocols. The probabilistic approach was particularly powerful in evaluating crossing fibers when present.
authors.affiliation: Functional MR Unit, Policlinico S. Orsola - Malpighi, Via Massarenti 9, Bologna, Italy.|Department of Biomedical and Neuromotor Sciences, University of Bologna, Via Foscolo 7, Bologna, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Testa
authors.affiliation: Functional MR Unit, Policlinico S. Orsola - Malpighi, Via Massarenti 9, Bologna, Italy.|Department of Biomedical and Neuromotor Sciences, University of Bologna, Via Foscolo 7, Bologna, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Evangelisti
authors.affiliation: Istituto Italiano di Tecnologia, Center for Neuroscience and Cognitive Systems@Unitn, Corso Bettini 31, Rovereto, Trento, Italy.|Center for Mind and Brain Sciences, University of Trento, Corso Bettini 31, Rovereto, Trento, Italy.
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Popeo
authors.affiliation: Functional MR Unit, Policlinico S. Orsola - Malpighi, Via Massarenti 9, Bologna, Italy.|Department of Biomedical and Neuromotor Sciences, University of Bologna, Via Foscolo 7, Bologna, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Zanigni
authors.affiliation: Functional MR Unit, Policlinico S. Orsola - Malpighi, Via Massarenti 9, Bologna, Italy.|Department of Biomedical and Neuromotor Sciences, University of Bologna, Via Foscolo 7, Bologna, Italy.
authors.forename: Laura Ludovica
authors.initials: LL
authors.lastname: Gramegna
authors.affiliation: Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, Bologna, Italy.|Centro Enrico Fermi, Roma, Piazza del Viminale 1, Rome, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Fantazzini
authors.affiliation: Functional MR Unit, Policlinico S. Orsola - Malpighi, Via Massarenti 9, Bologna, Italy.|Department of Biomedical and Neuromotor Sciences, University of Bologna, Via Foscolo 7, Bologna, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Tonon
authors.affiliation: Functional MR Unit, Policlinico S. Orsola - Malpighi, Via Massarenti 9, Bologna, Italy.|Department of Biomedical and Neuromotor Sciences, University of Bologna, Via Foscolo 7, Bologna, Italy.
authors.forename: David Neil
authors.initials: DN
authors.lastname: Manners
authors.affiliation: Functional MR Unit, Policlinico S. Orsola - Malpighi, Via Massarenti 9, Bologna, Italy. raffaele.lodi@unibo.it.|Department of Biomedical and Neuromotor Sciences, University of Bologna, Via Foscolo 7, Bologna, Italy. raffaele.lodi@unibo.it.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Lodi
mesh_terms: D000328:Adult; D000368:Aged; D016880:Anisotropy; D001921:Brain / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D003627:Data Interpretation, Statistical; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011712:Pyramidal Tracts / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Corticospinal tracts; Diffusion tractography; Healthy subjects