title: Corticospinal tractography with morphological, functional and diffusion tensor MRI: a comparative study of four deterministic algorithms used in clinical routine.
abstract: OBJECTIVE
  Diffusion tensor imaging permits study of white matter fibre bundles; however, its main limitation is lack of validation on anatomical data, especially in crossing fibre regions. Our study aimed to compare four deterministic tractography algorithms used in clinical routine. We studied the corticospinal tract, the bundle mediating voluntary movement. Our study seeks to evaluate tractography provided by algorithms through comparative analysis by expert neuroradiologists.
  
  
  METHODS
  MRI data from 15 right-handed volunteers (30.8 years) were studied. Regions of interest (ROIs) were segmented on morphological and functional MRI. Diffusion weighted images (15 directions) were performed, then for each voxel the tensor was estimated. Tractography of the corticospinal tract was performed using four fibre-tracking algorithms. Three numerical integration methods Euler, Runge-Kutta second (RK2) and fourth order (RK4), and a tensor deflection method (TEND). Quantitative measurement was performed. Qualitative evaluation was carried out by two expert neuroradiologists using Kappa test concordance.
  
  
  RESULTS
  For the quantitative aspect, only RK2 and TEND presented no significant difference concerning the number of fibres (p = 0.58). There was no difference between right and left side for each algorithm. Regarding the qualitative aspects, there was a lack of fibres from the ventrolateral part of the functional ROIs. Comparison by expert neuroradiologists revealed low rather than high concordance. The algorithm ranked first was RK2 according to expert preferences.
  
  
  CONCLUSIONS
  Different algorithms used in clinical routine failed to show realistic anatomical bundles. The most mathematically robust algorithm was not selected, nor was the algorithm defining more fibres. Validation of anatomical data provided by tractography remains a challenge.
authors.affiliation: IRISA Unité VisAGeS U746, INSERM/INRIA/CNRS/Université Rennes 1, Rennes, Cedex, 35043, France. romuald.seizeur@chu-brest.fr
authors.forename: Romuald
authors.initials: R
authors.lastname: Seizeur
authors.forename: Nicolas
authors.initials: N
authors.lastname: Wiest-Daessle
authors.forename: Sylvain
authors.initials: S
authors.lastname: Prima
authors.forename: Camille
authors.initials: C
authors.lastname: Maumet
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Ferre
authors.forename: Xavier
authors.initials: X
authors.lastname: Morandi
mesh_terms: D000328:Adult; D000465:Algorithms; D056324:Diffusion Tensor Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D011712:Pyramidal Tracts / Q000033:anatomy & histology*; D012016:Reference Values; D055815:Young Adult