References:

1

• Introduction
• Diffusion tensor imaging (DTI) has been applied
  to a great variety of neurological diseases and
  brain injuries. One of the problems that still
  faces this technology originates from the fact
  that tensors are difficult to visualize and the
  various scalar quantities that can be derived
  from the tensors eigenvalues and eigenvectors,
  like fractional anisotropy (FA), mean diffusivity
  (MD) or the linear, planar and spherical
  coefficient (see fig. 1), may or may not be
  appropriate for a given application. Here we
  extend DTI into the temporal domain by comparing
  such measures within sequences of scans obtained
  from subjects who suffered a concussion. In such
  scans we expect to find differences in the
  structural integrity of the white matter during
  the recovery period. We also propose an analysis
  technique that can lead to a better diagnosis and
  classification of the severity of mild traumatic
  brain injuries (MTBI).

For closer investigation, the vector fields
corresponding to the dominating eigenvalue for
the three scans in regions with LIgt0.2 are shown
in fig. 3 (right). Vectors plotted on top of each
other in red, green and blue show clear
differences in the region where the colors appear
in fig. 2, indicating a reorganization of the
white matter integrity over the time span of two
weeks.

• Conclusions
• Reorganization in the white matter is found in
  sequences of DTI scans taken within 24h of a
  concussion and about one and two weeks later
• The lattice index is a compelling measure for the
  comparison of the white matter integrity as is
  allows for a comparison of tensor properties in
  regions (not single voxels) therefore increasing
  the S/N ratio
• Color component encoding is a powerful tool to
  identify brain regions where the white matter
  integrity in a sequence of scans differs and may
  be a powerful diagnosic technique for detecting
  MTBI and recovery from MTBI.

• Methods
• DTI scans from College football players who
  suffered a concussion were taken within 24h of
  the injury with follow up scans about one and two
  weeks later
• Eigenvalues and eigenvectors of the diffusion
  tensor were calculated for each voxel using FSL
  1 and the three scans were co-registered using
  TBSS 2
• The lattice index together with a color component
  encoding scheme (see below) was used to identify
  regions where the scans show differences in the
  integrity of the white matter. In such a scheme
  the scans in the sequence are encoded by
  different colors thereby highlighting brain
  regions where structural changes over time take
  place as colored whereas areas that do not change
  appear gray
• In these regions additional analysis was
  performed by investigating the vector field
  that corresponds to the dominating eigenvalue.

References 1 S.M. Smith et al. (2004) Advances
in functional and structural MR image analysis
and implementation in FSL. Neuroimage
23208-219 2 S.M. Smith et al. (2006)
Tract-based spatial statistics Voxelwise
analysis of multi-subject diffusion data.
Neuroimage 311487-1505 3 C. Pierpaoli, P.J.
Basser (1996) Toward a quantitative assessment of
diffusion anisotropy. Magnetic Resonance in
Medicine 36893-906
Acknowledgement Work supported by NINDS grant
48299 (JASK).