Hi Anastasia,
> Are the
> individual FA
> maps registered to this template using the non-linear
> transform? Is it the
> same method as described for the older version of the TBSS?
Yes, all the native FA maps are registered to the FA template using non-linear registration (nreg, IRTK) with the same parameters than to the "best target". In the future version of TBSS, it will use FNIRT, our in-house non-linear registration.
> What was the rationale behind the introduction of FMRIB_58?
Mainly a time issue I would say, but Steve could correct me. We tested if using this high-resolution template would make any difference compared to selecting the best target. It showed that the final results, at least for the adolescent and adult populations we tested it on, were almost identical, thanks to the projection step that compensates for the residual misregistration.
> In the original
> version a real FA map was chosen because the average FA
> maps can be blurry.
> Has this problem been solved with FMRIB_58?
Absolutely. As you can see in fslview, this is a high-resolution template created from very high quality scans non-linearly iteratively registered (3 iterations, see http://www.fmrib.ox.ac.uk/fsl/tbss/FMRIB58_FA.html).
Hope this helps,
Gwenaelle
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