Hi - please see the FAQ:
http://www.fmrib.ox.ac.uk/fslfaq/#title_fast
Steve.
On 10 Jul 2007, at 23:11, Dianne Patterson wrote:
> Dear Group,
>
> I'm trying to understand how fast determines volumes of each tissue
> type.
> Below is a default segmentation of a partial brain (as defined by a
> basal ganglia roi).
> Presumably, Tissue 2 is WM.
> So, if I threshold the segmented image at 2.9, I should get back,
> the WM only mask...correct?
> Thus avwstats++ -V should give me the volume of white matter...
> But as you can see, the value fast gives me (3197.8) is similar to
> but does not match the value from avwstats++
> (3222.327881).
>
> I've seen this for whole brains as well...
> Why should such a difference exist?
>
> Thankyou for your time,
>
> Dianne
> =======================
>
> Write segmentation image /tmp/fsl_bOIYFH.fastout/QQQQQ_seg.hdr
> Successfully!
>
> Class: CSF tissue 1 tissue 2
> brain percentage
> Volumes: 42187.7 8504.8 3197.8
> 0.217156
>
>
> [dti_erp/e3131/WM_Seg] dpat% avwmaths++ bg_core_seg -thr 2.9 bg-
> core_seg_wm
>
> [dti_erp/e3131/WM_Seg] dpat% avwstats++ bg-core_seg_wm.nii.gz -V
>
> 1924 3222.327881
>
> --
> Dianne Patterson, Ph.D.
> [log in to unmask]
> ERP Lab
> University of Arizona
> 621-3256 (Office)
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR 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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