Geometrically constrained two-tensor model for crossing tracts in DWI


Sharon Peled, O. Friman, Ferenc Jolesz, C.-F. Westin
Magnetic Resonance Imaging
Volume 24, Pages 1263-1270
2006

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Abstract

MR diffusion tensor imaging (DTI) of the brain and spine provides a unique tool for both visualizing directionality and assessing intactness of white matter fiber tracts in vivo. At the spatial resolution of clinical MRI, much of primate white matter is composed of interdigitating fibers. Analyses based on an assumed single diffusion tensor per voxel yield important information about the average diffusion in the voxel but fail to reveal structure in the presence of crossing tracts. Until today, all clinical scans assume only one tensor, causing potential serious errors in tractography. Since high angular resolution imaging remains, so far, untenable for routine clinical use, a method is proposed whereby the single-tensor field is augmented with additional information gleaned from standard clinical DTI. The method effectively resolves two distinct tract directions within voxels, in which only two tracts are assumed to exist. The underlying constrained twotensor model is fitted in two stages, utilizing the information present in the single-tensor fit. As a result, the necessary MRI time can be drastically reduced when compared with other approaches, enabling widespread clinical use. Upon evaluation in simulations and application to in vivo human brain DTI data, the method appears to be robust and practical and, if correctly applied, could elucidate tract directions at critical points of uncertainty.

Results from in vivo DTI. (A) A region of interest in the brain - enlarged in the rest of the figure. (B) Single-tensor analysis: the direction of the first eigenvector. Vectors with a significant through-plane component are indicated by circles. (C) Single-tensor planar index, Cp. Panels D to F show results from the two-tensor model. (D) First direction. (E) Fraction of smaller tract. (F) Second direction.

Reference

Peled S, Friman O, Jolesz F, Westin CF. Geometrically constrained two-tensor model for crossing tracts in DWI. Magnetic Resonance Imaging 2006;24:1263-1270.

Bibtex entry

@article{peledMRI06,
  author         = {Sharon Peled and Ola Friman and Ferenc Jolesz and          
                   Carl-Fredrik Westin},
                                      
  title          = {Geometrically constrained two-tensor model for crossing    
                   tracts in {DWI}},
                                          
  year           = {2006},
                                                    
  journal        = {Magnetic Resonance Imaging},
                              
  volume         = {24},
                                                      
  pages          = {1263--1270},
}

Grants

NIH P41-RR13218 (NAC), NIH U24-RR021382

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