Yes, very thank you very much...
Julio
On Oct 6 2010, Stamatios Sotiropoulos wrote:
>Dear Julio,
>
>It is not meaningful to compare the second eigenvector of dtifit with the
>second fibre estimate of bedpostx.
>
>Dtifit performs the DTI-single tensor model regression and V2 will be the
second axis of the fitted ellipsoid. Only V1 can be directly interpreted
as
a fibre orientation, therefore dtifit can resolve one orientation per
voxel.
>
>Bedpostx fits a multi-tensor model (i.e. many ellipsoids) with some
geometrical constraints on each tensor. Each dyad corresponds to a
different
>fibre orientation and a different compartment of the model. Whereas V1, V2
>and V3 from dtifit, all refer to the same model compartment.
>
>Hope this is helpful,
>Stam
>
>----- Original Message -----
>From: "Julio Duarte" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Wednesday, October 06, 2010 9:40 PM
>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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