Hi Tyler,
1) Eddy_correct is based on a simple model for eddy current artifacts that include scaling, translation and shear of the images. All these artifacts, including head motion can be captured by an affine transformation. That's why eddy_correct uses 12 DOFs rather than 6, which would only correct for head motion.
2) The link "FDT theory" on the FDT webpage describes how bedpostx and probtrackx work. For dtifit there is no much theory, it is a simple least squares fit of the linear DTI model. Peter Basser's first DTI papers (any many other review papers since then) have all the information you need.
Hope this helps,
Stam
On 20 May 2011, at 13:02, Tyler wrote:
> Hello FSL Kingdom, hopefully someone can help me out with two specific questions.
>
> 1) Regarding the naming and function of the command eddy_correct: If all the command does is register the diffusion images to the reference image (12-degree of freedom affine), can this be considered an eddy-current correction?
>
> Granted it is important to align the diffusion images to a reference image before fitting a tensor, but how would one directly address the issue of correcting for eddy distortions independent of head motion? Does FSL have this capability?
>
> 2) As a secondary question, where can I find more detailed information about the FDT pipeline? The general information on the fsl webpage doesn't really provide enough information about the tools (e.g., how does the dtifit command calculate the FA/MD images).
>
> PS: I'm sorry if these posts have already been covered... I searched the archives but didn't come up with a direct answer.
>
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