2008 Winter Project Week Tractography Meeting Notes

Notes from Presentations and Discussions

Data quality, NAMIC DTI pipeline

• Issues?
• Create a synthetic tensor data set (Gordon's helix, crossing fiber situation). Good for debugging for comparing methods.
• EPI distortion correction, ITK?
• White matter mask? Generous?
• Freesurfer white matter mask? Map structural segm to DTI
• EM segmenter in Slicer white matter mask?

ROI definitions and impact on different methods

• Force all methods to use the same ROIs?
• Classes of ROIs?
• For streamline methods larger ROIs than the tract itself good
• For shortest path methods, connections stop at ROI

Methods:

• Streamline, Slicer2 (Sonia)
• Streamline, whole brain Slicer2 (Sonia)
• Streamline, Fiberviewer (Casey)
• Streamline, Gtract (Vince)

• Shortest path (Fast Marching), volumetric (Vince)
• Stochastic, volumetric Slicer3 (Tri)
• Shortest path, volumetric (John)
• Shortest path, volumetric (Tom)

Review and define metrics to compare results, which methods to compare?

Current metrics: tensor invariants (FA, trace, mode, norm), volume, length.

What is a good fiber tract?

Easier question: How similar are two methods?

Parameter settings within a method may change the results comparable to the difference between methods.

• 12 different tracts
• Tracts voxelized -> volumetric result from tracts
• Missing parts of a tract, how should be penalized?
• Statistics along the tracts, should we sum along the tract to get one measure?
• Distributions across the tract
• Atlas (Casey)

• Bundle thickness: mix of radius of tract and uncertainty
• How to define volume from connectivity map (shortest path, or stochastic)

Scientific Output

• All groups should report volumes in unit ml