Intracranial Volume and DTI / NODDI Metrics

1

Hi everyone,

I have read that metrics such as FA tend to covary with brain volume. Related to this, I have two questions:

  1. Given the non-specificity of FA, is there a good intuition for why FA and brain volume would covary?
  2. Are there any global biasses in other DTI / NODDI metrics that would motivate regressing out brain volume for other DWI measures?

Best,
Steven

2

Can you describe what do you mean by “brain volume”?

3

Total intracranial volume as indexed by FreeSurfer eTIV, for example.

1 Like
4

Hmm, I think I don’t know enough to answer this then. I am a bit surprised similar to you that FA covaries with brain volume. I cannot think of a straightforward reason about why this should be the case.

5

We have observed the effect of eTIV on both DTI and NODDI metrics in large-scale cohorts (Frontiers | Age-Related Changes of Peak Width Skeletonized Mean Diffusivity (PSMD) Across the Adult Lifespan: A Multi-Cohort Study and Frontiers | Age-Related Variations in Regional White Matter Volumetry and Microstructure During the Post-adolescence Period: A Cross-Sectional Study of a Cohort of 1,713 University Students, in supplement), but it was more explicitly described by a recent study here (https://onlinelibrary.wiley.com/doi/10.1002/hbm.26093).

I’m also curious to know why we observe such dependency on the brain volume, if anyone has any hypothesis…!