Difference between revisions of "Projects:MultiTensorTractography"

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We describe a unified framework to simultaneously estimate multiple fibers at
 
We describe a unified framework to simultaneously estimate multiple fibers at
 
each location and perform tractography. Existing techniques estimate the local fiber orientation at each voxel
 
each location and perform tractography. Existing techniques estimate the local fiber orientation at each voxel
independently so there is no running knowledge of confidence in the
+
independently. Consequently, there is no running knowledge of confidence in the
estimated fiber model. We formulate fiber tracking as recursive estimation: at each step of tracing
+
estimated fiber model. We formulate fiber tracking as a recursive estimation: At each step of tracing
 
the fiber, the current estimate is guided by the previous.
 
the fiber, the current estimate is guided by the previous.
  
 
To do this we model the signal as either a weighted mixture of Gaussian tensors or
 
To do this we model the signal as either a weighted mixture of Gaussian tensors or
 
Watson directional functions and
 
Watson directional functions and
perform tractography within a filter framework. Starting from a seed point,
+
perform tractography within a filter framework. Starting from a seed point, the
 
fiber is traced to its termination using an unscented Kalman filter to
 
fiber is traced to its termination using an unscented Kalman filter to
 
simultaneously fit the local model and propagate in the most consistent
 
simultaneously fit the local model and propagate in the most consistent
direction.  Further, we modify the Kalman filter to enforce model, i.e., positive eigenvalues and convex weights.  Despite the
+
direction.  Further, we modify the Kalman filter to enforce the model, i.e., positive eigenvalues and convex weights.  Despite the
 
presence of noise and uncertainty, this provides a causal estimate of the
 
presence of noise and uncertainty, this provides a causal estimate of the
 
local structure at each point along the fiber.
 
local structure at each point along the fiber.
Line 18: Line 18:
 
Synthetic experiments demonstrate that this approach significantly improves
 
Synthetic experiments demonstrate that this approach significantly improves
 
the angular resolution at crossings and branchings while consistently
 
the angular resolution at crossings and branchings while consistently
estimating the mixture weights. ''In vivo'' experiments confirm the
+
estimating the mixture weights. ''In vivo'' experiments confirm the
 
ability to trace out fibers in areas known to contain such crossing and
 
ability to trace out fibers in areas known to contain such crossing and
 
branching while providing inherent path regularization.
 
branching while providing inherent path regularization.
Line 35: Line 35:
 
* J. Malcolm, M. E. Shenton, Y. Rathi. Two-Tensor Tractography Using a Constrained Filter. MICCAI, Pages 894-902, 2009  [http://pnl.bwh.harvard.edu/pub/papers_html/Malcolm-MICCAI2009.html (see here for the reference)].
 
* J. Malcolm, M. E. Shenton, Y. Rathi. Two-Tensor Tractography Using a Constrained Filter. MICCAI, Pages 894-902, 2009  [http://pnl.bwh.harvard.edu/pub/papers_html/Malcolm-MICCAI2009.html (see here for the reference)].
  
* J. Malcolm, O. Michailovich, S. Bouix, C.F. Westin, M. E. Shenton, Y. Rathi  A filtered approach to neural tractography using the Watson directional function. Med Image Analysis, Volume 14, Pages 58-69 2010  [http://pnl.bwh.harvard.edu/pub/papers_html/MalcolmMedImage10.html (see here for the reference)].
+
* J. Malcolm, M. Kubicki, M. E. Shenton, Y. Rathi. The effect of local fiber model on population studies. Workshop on Diffusion modeling (MICCAI), Pages 33-40, 2009  [http://jgmalcolm.com/ (see here for the reference)].
 +
 
 +
* J. Malcolm, O. Michailovich, S. Bouix, C.F. Westin, M. E. Shenton, Y. Rathi  A filtered approach to neural tractography using the Watson directional function. Med Image Analysis, Volume 14, Pages 58-69 2010  [http://pnl.bwh.harvard.edu/pub/papers_html/MalcolmMedImage10.html (see here for the reference)]

Latest revision as of 10:58, 14 May 2010

Home < Projects:MultiTensorTractography

Multi Tensor Tractography

We describe a unified framework to simultaneously estimate multiple fibers at each location and perform tractography. Existing techniques estimate the local fiber orientation at each voxel independently. Consequently, there is no running knowledge of confidence in the estimated fiber model. We formulate fiber tracking as a recursive estimation: At each step of tracing the fiber, the current estimate is guided by the previous.

To do this we model the signal as either a weighted mixture of Gaussian tensors or Watson directional functions and perform tractography within a filter framework. Starting from a seed point, the fiber is traced to its termination using an unscented Kalman filter to simultaneously fit the local model and propagate in the most consistent direction. Further, we modify the Kalman filter to enforce the model, i.e., positive eigenvalues and convex weights. Despite the presence of noise and uncertainty, this provides a causal estimate of the local structure at each point along the fiber.

Synthetic experiments demonstrate that this approach significantly improves the angular resolution at crossings and branchings while consistently estimating the mixture weights. In vivo experiments confirm the ability to trace out fibers in areas known to contain such crossing and branching while providing inherent path regularization.


Case01045 2T tc.png

Key Investigators

  • Brigham & Women's Hospital: Y. Rathi, J. Malcolm, Sylvain Bouix, Marek Kubicki, Martha E. Shenton, Carl-Fredrik Westin.
  • University of Waterloo: O. Michailovich

Publications

  • J. Malcolm, M. E. Shenton, Y. Rathi. Neural tractography using an unscented Kalman filter. Inf Process Med Imaging,Volume 21, Pages 126-138, 2009 (see here for the reference).
  • J. Malcolm, M. E. Shenton, Y. Rathi. Two-Tensor Tractography Using a Constrained Filter. MICCAI, Pages 894-902, 2009 (see here for the reference).
  • J. Malcolm, M. Kubicki, M. E. Shenton, Y. Rathi. The effect of local fiber model on population studies. Workshop on Diffusion modeling (MICCAI), Pages 33-40, 2009 (see here for the reference).
  • J. Malcolm, O. Michailovich, S. Bouix, C.F. Westin, M. E. Shenton, Y. Rathi A filtered approach to neural tractography using the Watson directional function. Med Image Analysis, Volume 14, Pages 58-69 2010 (see here for the reference)