Hi - yes, the article is more about the theory behind SIENA/SIENAX than
all the practical details, it just mentions briefly that SIENAX uses
partial volume estimation (ie voxel tissue-type probabilities) to maximise
the accuracy of total volume estimation.
No threshold is used in estimating total volume for a given tissue type;
this is not necessary. Instead, each voxel's partial volume estimate for a
given tissue type is added with each other voxel's estimate, to give a
total volume estimate.
Thanks, Steve.
On Wed, 27 Nov 2002, Giorgos Karas wrote:
> Dear list,
> in trying to understand how SIENAX calculates which voxels are
> included during the volume estimation, I could not help noticing that
> segmented maps are written as probability maps.
>
> Question: is there a threshold when estimating volume from these maps,
> do partial volume maps play a role?
>
> I read the articles many times, but it is not clear to me what is going on.
>
> Any help would be appreciated.
>
> thank you,
>
> Giorgos
>
> GB Karas, MD
> Vrije Universiteit Medical Centre - Image Analysis Centre
> Department of Radiology - Postbus 7057 -1007 MB Amsterdam
> The Netherlands
> Tel: +31 20 4443616 - Fax: + 31 20 4041945
>
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
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