Hi Stefano,
> I have another question regarding eddy: why is it that one has to collect data on the whole sphere, rather than the top half of the sphere?
the best information with regards to EC distortions comes from volumes with similar contrast and different EC distortions. If I have two volumes obtained with diffusion directions g1 and g2 and where the angle between g1 and g2 is some "small" number phi (say 5 degrees) then these volumes will have similar contrast (which is good) but on the other hand they are likely to also have similar EC distortions (which means there is little to learn about the distortions by comparing them).
If on the other hand the angle between g1 and g2 is 180-phi the images will still have similar contrast, but now the EC distortions are very different and there is a lot of information about the distortions in their comparison.
Hope that is clear?
Jesper
>
> Stefano Marenco, MD
> NIMH/CBDB
> 10 Center Drive, Bldg 10 room 3C103
> Bethesda MD 20892
> Tel 301 435-8964
> Fax 301 480-7795
> Email: [log in to unmask]
>
>
> -----Original Message-----
> From: Darren G [mailto:[log in to unmask]]
> Sent: Thursday, September 27, 2012 9:49 AM
> To: [log in to unmask]
> Subject: [FSL] Re-asking about eddy and bvecs
>
> Dear List
>
> Does using the new eddy program require or allow one to adjust bvecs for the results of eddy (similar to what rotate_bvecs did previously)?
>
> When eddy finishes it outputs the corrected volumes and a file called <basename>.eddy_parameters. which appears to be in size the number of scans (rows) x 16 (columns). What do the columns mean?
>
> Does that file contain the parameters to adjust the bvecs, and is there a script for doing so?
>
> Thanks
> Darren
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