Thank you for your reply - one more quick question on the issue - can you
give me a basic idea of how the PBMAP's are converted into PVE's?
Thanks again for your help
Mike
On Sun, 30 Nov 2003, Stephen Smith wrote:
> Hi - yes you can think of a PVE image as telling you the estimate of the
> fraction of a voxel's volume occupied by that tissue type.
>
> Your second question raises some of the philosophical issues relating to
> VBM, but I think the simplest answer is that yes it is doing what you
> think it is doing.
>
> Cheers.
>
>
> On Fri, 28 Nov 2003, Mike Milham wrote:
>
> > Hi! I have been using FSL's tools for VBM analyses and have the following
> > question - I'm sorry if this may seem obvious, but I wanted to be sure on
> > this one - If I understand the pve maps in FSL correctly, they appear to
> > be equivalent to the modulated data that is becoming increasingly common in
> > the SPM world - as they both appear to be able to provide voxel-wise volume
> > measurements? Am I correct about this or am I misinterpreting something?
> >
> > If so, then if I run through a vbm-like path using the PVE's and toss in
> > total gray matter as a covariate in my model (to correct for diffs
> > resulting from differences in intra-cranial volume and/or those introduced
> > by normalization), then am I correct in assuming that my differences can be
> > legitimately interpreted as differences in voxel-wise volume?
> >
> > Thanks
> > Mike
> >
>
> Stephen M. Smith DPhil
> Associate Director, FMRIB and Analysis Research Coordinator
>
> Oxford University Centre for Functional MRI of the Brain
> John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
> +44 (0) 1865 222726 (fax 222717)
>
> [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
>
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