title: Visualizing Hyolaryngeal Mechanics in Swallowing Using Dynamic MRI.
abstract: BACKGROUND
  Coordinates of anatomical landmarks are captured using dynamic MRI to explore whether a proposed two-sling mechanism underlies hyolaryngeal elevation in pharyngeal swallowing. A principal components analysis (PCA) is applied to coordinates to determine the covariant function of the proposed mechanism.
  
  
  METHODS
  Dynamic MRI (dMRI) data were acquired from eleven healthy subjects during a repeated swallows task. Coordinates mapping the proposed mechanism are collected from each dynamic (frame) of a dynamic MRI swallowing series of a randomly selected subject in order to demonstrate shape changes in a single subject. Coordinates representing minimum and maximum hyolaryngeal elevation of all 11 subjects were also mapped to demonstrate shape changes of the system among all subjects. MophoJ software was used to perform PCA and determine vectors of shape change (eigenvectors) for elements of the two-sling mechanism of hyolaryngeal elevation.
  
  
  RESULTS
  For both single subject and group PCAs, hyolaryngeal elevation accounted for the first principal component of variation. For the single subject PCA, the first principal component accounted for 81.5% of the variance. For the between subjects PCA, the first principal component accounted for 58.5% of the variance. Eigenvectors and shape changes associated with this first principal component are reported.
  
  
  CONCLUSIONS
  Eigenvectors indicate that two-muscle slings and associated skeletal elements function as components of a covariant mechanism to elevate the hyolaryngeal complex. Morphological analysis is useful to model shape changes in the two-sling mechanism of hyolaryngeal elevation.
authors.affiliation: Department of Cellular Biology & Anatomy, Medical College of Georgia, Georgia Regents University, 1120 15th Street, CB-1101, Augusta, GA 30912, USA ; Department of Otolaryngology, Medical College of Georgia, Georgia Regents University, 1120 15th Street, CB-1101, Augusta, GA 30912, USA.
authors.forename: William G
authors.initials: WG
authors.lastname: Pearson
authors.affiliation: Department of Anatomy and Neurobiology, Boston University School of Medicine, 72 E. Concord Street, L-1004, Boston, MA 02118, USA.
authors.forename: Ann C
authors.initials: AC
authors.lastname: Zumwalt
keywords: Deglutition; Hyolaryngeal complex; Imaging and Visualization in Biomechanics; Medical Imaging and Visualization; Morphometrics
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