Hi Susie,
> Hello,
> I am working with a data set of 50 subjects and am
> attempting to analyze the
> 12-directional DTI data. I have been told that 12
> directions is not enough
> to perform tractography--is this true?
I am not the best person to answer this question, but I would think that the problem is that you would not be able to model more than one single fibre population in each voxel with this dataset.
So, provided that you would not be looking at tracts with a complex architecture (e.g. crossing other tracts), or just looking at the "core" of it (cf corpus callosum, cingulum bundle), this should be ok... Anybody else's got a take on this?
> Assuming that it is unwise/unreliable for me to conduct
> tractography on the
> 12-dir DTI set, I was wondering if it is possible to use
> TBSS to perform a
> similar analysis. What I am proposing is:
> 1. Mean FA skeleton from 50 subjects is generated
> using TBSS tools.
> 2. Skeleton is masked with tract of interest from
> probabilistic atlas.
> 3. Mean FA is found for skeleton voxels within the
> mask for each subject,
> representing an estimate of the FA in the cingulate gyrus
> for example.
>
> Is this defensible?
This sounds sensible to me *as long as* you are aware that the vast majority of the voxels in the WM is a mixture of different tracts (as you can see if you turn on some of the WM atlases in fslview, see also Behrens et al., 2007). So this is true also with the voxels of the skeleton to some extent, but this still would be a good approximation.
This approach would lead to absolutely unambiguous results for regions like the cingulum bundle, or the most "midsagittal" part of the fornix and corpus callosum etc.
Hope this makes sense,
Gwenaëlle
|