title: MR tractography based on directional diffusion function validation in somatotopic organization of the pyramidal tract.
abstract: OBJECTIVE
  Conventional tractography based on the "streamline" method only partially visualizes the pyramidal tract because of fiber crossing with other white matter tracts. Recently a new tractography method based on directional diffusion function (DDF) has been proposed. This method was reported to visualize the pyramidal tract to a larger extent than conventional techniques do. To validate the DDF-based tractography method, we studied the somatotopic organization of the pyramidal tract in the posterior limb of the internal capsule (PLIC).
  
  
  METHODS
  Pyramidal tracts in the intact hemispheres of 14 brain tumor patients were drawn using the directional diffusion function-based tractography method. Each pyramidal tract was divided into four fiber bundles according to the cephalocaudal positions of their termination in the precentral gyrus. The cephalocaudal positions in the precentral gyrus of the four fiber bundles were correlated with their positional relationships in the PLIC along the mediolateral and anteroposterior axes.
  
  
  RESULTS
  Fiber bundles terminating more caudally in the precentral gyrus were located significantly more anteriorly in the PLIC (r = 0.59, Spearman's correlation coefficient, P < .0001). On the other hand, no significant correlation was shown between the cephalocaudal positions in the precentral gyrus of the four fiber bundles and their relative positions in the PLIC along the mediolateral axis.
  
  
  CONCLUSIONS
  Estimated organization of the fiber bundles of the pyramidal tract in the PLIC was consistent with anatomically known somatotopic organization, which supported the validity of the DDF-based tractography method.
authors.affiliation: Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. tyoshiu@med.kyushu-u.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshiura
authors.forename: Seiji
authors.initials: S
authors.lastname: Kumazawa
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Noguchi
authors.forename: Akio
authors.initials: A
authors.lastname: Hiwatashi
authors.forename: Osamu
authors.initials: O
authors.lastname: Togao
authors.forename: Koji
authors.initials: K
authors.lastname: Yamashita
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Arimura
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Higashida
authors.forename: Fukai
authors.initials: F
authors.lastname: Toyofuku
authors.forename: Futoshi
authors.initials: F
authors.lastname: Mihara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Honda
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000033:anatomy & histology* / Q000473:pathology; D001932:Brain Neoplasms / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D011712:Pyramidal Tracts / Q000033:anatomy & histology* / Q000473:pathology