title: Morphometrics of the entire human spinal cord and spinal canal measured from in vivo high-resolution anatomical magnetic resonance imaging.
abstract: METHODS
  Measurements of cervical and thoracolumbar human spinal cord (SC) geometry based on in vivo magnetic resonance imaging and investigation of morphological "invariants."
  
  
  OBJECTIVE
  The current work aims at providing morphological features of the complete in vivo human normal SC and at investigating possible "invariant" parameters that may serve as normative data for individualized study of SC injuries.
  
  
  BACKGROUND
  Few in vivo magnetic resonance image-based studies have described human SC morphology at the cervical level, and similar description of the entire SC only relies on postmortem studies, which may be prone to atrophy biases. Moreover, large interindividual variations currently limit the use of morphological metrics as reference for clinical applications or as modeling inputs.
  
  
  METHODS
  Absolute metrics of SC (transverse and anteroposterior diameters, width of anterior and posterior horns, cross-sectional SC area, and white matter percentage) were measured using semiautomatic segmentation of high resolution in vivo T2*-weighted transverse images acquired at 3 T, at each SC level, on healthy young (N = 15) and older (N = 8) volunteers. Robustness of measurements, effects of subject, age, or sex, as well as comparison with previously published postmortem data were investigated using statistical analyses (separate analysis of variance, Tukey-HSD, Bland-Altman). Normalized-to-C3 parameters were evaluated as invariants using a leave-one-out analysis. Spinal canal parameters were measured and occupation ratio border values were determined.
  
  
  RESULTS
  Metrics of SC morphology showed large intra- and interindividual variations, up to 30% and 13%, respectively, on average. Sex had no influence except on posterior horn width (P < 0.01). Age-related differences were observed for anteroposterior diameter and white matter percentage (P < 0.05) and all postmortem metrics were significantly lower than in vivo values (P < 0.001). In vivo normalized SC area and diameters seemed to be invariants (R > 0.74, root-mean-square deviation < 10%). Finally, minimal and maximal occupation ratio were 0.2 and 0.6, respectively.
  
  
  CONCLUSIONS
  This study presented morphological characteristics of the complete in vivo human SC. Significant differences linked to age and postmortem state have been identified. Morphological "invariants" that could be used to calculate the normally expected morphology accurately, were also identified. These observations should benefit to biomechanical and SC pathology studies.
  
  
  METHODS
  N/A.
authors.affiliation: *Department of Mechanical Engineering, École de technologie supérieure, Montreal, Quebec, Canada †Department of Medical Engineering, Research Center, Hôpital du Sacré-Cœur de Montréal, Montreal, Quebec, Canada ‡Laboratoire de Biomécanique Appliquée, Aix-Marseille Université, IFSTTAR-, Faculté de Médecine secteur Nord, Marseille, Cedex, France; and §Centre de Résonance Magnétique Biologique et Médicale (CRMBM), Aix-Marseille Université, CNRS, Marseille, France.
authors.forename: Léo
authors.initials: L
authors.lastname: Fradet
authors.forename: Pierre-Jean
authors.initials: PJ
authors.lastname: Arnoux
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Ranjeva
authors.forename: Yvan
authors.initials: Y
authors.lastname: Petit
authors.forename: Virginie
authors.initials: V
authors.lastname: Callot
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013115:Spinal Canal / Q000033:anatomy & histology*; D013116:Spinal Cord / Q000033:anatomy & histology*; D055815:Young Adult