Hi Steve,

Many thanks for your prompt reply on the weekend!

WW
----- Original Message -----
From: "Stephen Smith" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, October 13, 2002 9:31 PM
Subject: Re: [FSL] Intracranial volume calculation


> You are right that SIENAX bypasses the problem of differentiating CSF and
> skull by normalising using head size (via registration to the MNI152)
> instead od W+G+CSF.
>
> You CAN find the estimated CSF volume by running avwstats on the pve_0
> image but as you point out in cases of severe atrophy some peripheral CSF
> will get disregarded this way.
>
> Your other suggestion is also a possibility - if you divide the MNI152
> "ICV" (on the basis of adding up the standard space apriori maps and
> thresholding at totalP=0.5 I have just estimated this as 1847712 mm^3) by
> the SIENAX volumetric scaling factor then you could use that.
>
> Regards, Steve.
>
> On Sat, 12 Oct 2002, Wei Wen wrote:
>
> > Hi FSL team,
> >
> > To avoid the difficult task of separating CSF/skull, sienax normalizes
brain
> > volume with respect to a standard. This approach is good for many
> > applications such as atrophy detection etc. However, if I do wish to
have
> > intracranial volume as a denominator to normalise some other
measurements,
> > what should I do then? Since CSF estimation may not be terribly robust,
one
> > may want to use some methods other than just the sum of CSF, GM and WM.
With
> > sienax, the scaling factor is worked out. If we have the ICV of the
standard
> > brain that sienax uses in generating the scaling factor with, then we
should
> > be able to work out ICV of an individual brain. Am I correct or not? Any
> > better method? If it is possible, then where do I find ICV of the
standard
> > brain (MNI 152 brain?)? The mean of those 152 brains' ICV? Please give
me
> > some clues?
> >
> > Many thanks and regards,
> >
> > Wei Wen
> > UNSW/Australia
> >
>
>  Stephen M. Smith
>  Head of Image Analysis, FMRIB
>
>  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