Hi,
the weighting is according to (Salvador et al, HBM, 2005, 144-155).
Unfortunately, there is no such thing with a 4D mask in dtifit.
Cheers,
Stam
----- Original Message -----
From: "bettyann BA" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, February 08, 2011 4:32 AM
Subject: Re: [FSL] Mask out artifacts in DTI processing?
What sort of weighted fitting is done with the --wls option? I see that
RESTORE (Chang et al, MRM, 2005) uses an iterative reweighted least-squares
regression algorithm. Is there a way to see the final weighting of each
voxel that went into the FA calculation?
Independent of the --wls option, I would like a way to specify, on an
voxel-by-voxel and gradient-by-gradient basis, whether or not a voxel should
be used in the FA calculation. I would like to omit artifactual voxels
caused by a vitamin E capsule. Perhaps a 4D mask would allow me to do this.
Rather than using the same 3D b0 mask for all subvolumes within the 4D DWI
volume, an option to use a 4D mask for the 4D DWI volume would give me the
flexibility I am looking for. For greatest flexibility, I suppose this mask
could be a floating point weight rather than a binary [0,1] mask. But a
binary mask would be allow me to drop artifactual voxels without dropping
the entire gradient and without dropping the entire region across all
gradients.
thanks.
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