I'm not sure what you are trying to do, but the eigenvectors are constrained
to be orthogonal, whereas the fibers that bedpostx reconstructs are not.
The first fiber should be parallel to the first eigenvector in most cases,
but this definitely does not hold true for subsequent fibers.
Peace,
Matt.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Julio Duarte
Sent: Wednesday, October 06, 2010 3:41 PM
To: [log in to unmask]
Subject: [FSL] BedpostX vs dtifit
Dear FSL experts,
I'm comparing the error histograms for the masked dyads2 (threshold 0.05)
obtained with bedpostX and second eigenvector (_V2) on the same voxels using
dtifit after registering 2 images. BedpostX errors (relative to the
reference image) below 60 degrees are consistently lower in frequency than
those computed using dtifit, but after 60 degrees the BedpostX errors are
consistently higher in frequency than those obtained with dtifit. On the
other hand, comparing the error histogram for dyads1 from BedpostX vs first
eigenvector from dtifit are very similar (as I expected).
Have you ever compared these 2 methods along the second eigenvectors? Do
these results have an explanation?
Julio
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