Fixel based analysis and Anatomically-constrained Tractography

Hi all,

I am running a fixel-based analysis as a beginner and have a conceptual question about the workflow.

Once I generate to Fiber Orientation Densities (FODs) , the suggested workflow is to generate a group FOD template, register all participant data to the template and generate whole brain tractography in the FOD template space. However, in my initial individual participant workflow, I used the T1 image to generate anatomically-constrained tractography (ACT). I am confused why the ACT step is omitted in the FOD template - group workflow. Does wm_fod ensure that the FOD generated are restricted to tracts originating/terminating at white matter regions?

Thanks,
Hasini

Hi Hasini,

My understanding is that the fixel-based pipeline is completely different from the ACT and rely on different types of information. The fibre orientation estimates of the FOD (and the constrained spherical deconvolution) give information about crossing fibres which is not accounted for in the ACT which rely more on tissue segmentations/prior maps.

Charly

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