Mark,
Ah, thanks. This helps a great deal.
The values I calculate for the tissue classifications are still not exactly the same as what I see
reported in the *.sienax file. The final brain percentage value does match, however. Might you
see something I am doing wrong? i used fsl v3.3 when running sienax but fsl v4.0.1 for fslstats
(which gives the same values as avwstats++ v3.3).
% fslstats 20071129_13_1_stdmaskbrain_pve_0 -m -v
0.050224 7864320 6308232.500000
% fslstats 20071129_13_1_stdmaskbrain_pve_1 -m -v
0.081942 7864320 6308232.500000
% fslstats 20071129_13_1_stdmaskbrain_pve_2 -m -v
0.060950 7864320 6308232.500000
in matlab:
>> csf = 0.050224 * 6308232.500000;
>> grey = 0.081942 * 6308232.500000;
>> white = 0.060950 * 6308232.500000;
>> bpf = ( grey + white ) / ( grey + white + csf )
bpf = 0.7399
>> fprintf( 'csf = %.1f grey = %.1f white = %.1f \n', csf, grey, white );
csf = 316824.7 grey = 516909.2 white = 384486.8
The tissue volumes in my *.sienax file are:
Class: CSF tissue 1 tissue 2 brain percentage
Volumes: 316748.7 516990.9 384503.5 0.739996
Also, in the snippet of code from the sienax script where the volumes are computed, are you
dividing the result by 1 in the dc calculator? if so, why?
Thank you for your help,
- BettyAnn
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