I have 3 questions related to FAST and SIENAX
Re FAST: While this link http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/FAST/FAQ indicates that extracting a good estimate of CSF should involve use of a T2 (rather than T1) to obtain maximum contrast between skull and CSF, I assume an accurate sum of total intracranial volume (TIV) be calculated from a T1 by simply summing the 3 partial volume estimates of all three tissue type, CSF, GM and WM? That a T1 is sufficient is indicated by the FAST practical. I would expect that the TIV would include the meninges. Are both of these assumptions correct?
Re Sienax: Sienax is indicated for total brain tissue volume estimation in pathology, such as Alheimers. Is this referring to TIV or just the GM and WM (in some contexts CSF and also referred to as a tissue). The practical ( https://fsl.fmrib.ox.ac.uk/fslcourse/lectures/practicals/seg_struc/index.html#sienax ) suggests that Sienax takes TIV (CSF, GM, WM) but extracts just the GM/WM total combined volume. Is this correct?
I have two groups: 10 patients with intermediate stage Parkinson’s Disease (PD) and 10 controls. I want to treat TIV as a nuisance covariate and remove is contribution to VBM cortical and FIRST subcortical estimates. I would assume FAST could be applied to both PD and controls to arrive at TIV estimates that could be run in an ANCOVA model to eliminate contribution to the VBM and FIRST outcomes?
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