Yes, the difference is not large. I was mostly concerned that I was doing something incorrectly.
Thanks especially for the initial reply as that set me right.
Best,
- BettyAnn
On Wed, 2 Jan 2008 22:45:00 +0000, Mark Jenkinson <[log in to unmask]> wrote:
>Hi,
>
>As these results are within 0.02% (not 2%, but 0.02%) of each other
>then that is far less than the accuracy to which these methods work.
>
>There was a slight numerical rounding error in the old version of
>avwstats (no ++) when accumulating over large images. The newer
>version of fslstats (which is almost identical to avwstats++ for these
>features) should be more accurate. However, both are fine with
>respect to numbers for siena and much less than the noise effects.
>
>All the best,
> Mark
>
>
>
>On 2 Jan 2008, at 22:15, Bettyann Chodkowski wrote:
>
>> Dear All,
>>
>> I think I found the source of the discrepancy. Currently I am
>> using FSL v3.3.
>>
>> avwstats -v (no ++) returns a *slightly* different volume value
>> than avwstats++
>> fslstats (v4.0.1) returns the same volume value as avwstats++
>>
>> When I use avwstats (no ++), i get nearly identical numbers as to
>> what is in the *.sienax file:
>>
>> % avwstats 20071129_13_1_stdmaskbrain_pve_0 -m -v
>> 0.050212 7864320 6308232.703233
>> % avwstats 20071129_13_1_stdmaskbrain_pve_1 -m -v
>> 0.081955 7864320 6308232.703233
>> % avwstats 20071129_13_1_stdmaskbrain_pve_2 -m -v
>> 0.060953 7864320 6308232.703233
>>
>>>> csf = 0.050212 * 6308232.703233;
>>>> grey = 0.081955 * 6308232.703233;
>>>> white = 0.060953 * 6308232.703233;
>>>> bpf = ( grey + white ) / ( grey + white + csf );
>>>> fprintf( 'csf = %.1f grey = %.1f white = %.1f bpf=%.6f \n',
>>>> csf, grey, white, bpf );
>> csf = 316749.0 grey = 516991.2 white = 384505.7 bpf=0.739996
>>
>> From *.sienax file:
>> Class: CSF tissue 1 tissue 2
>> brain percentage
>> Volumes: 316748.7 516990.9 384503.5
>> 0.739996
>>
>> Results from avwstats++ are below, but bottom line:
>> csf = 316824.7 grey = 516909.2 white = 384486.8 bpf = 0.7399
>>
>> I believe that the results generated from sienax/FSL v3.3 would be
>> slightly different from
>> sienax/FSL v4.0.1 due to the use of avwstats v fslstats, respectively.
>>
>> Is this something you see, too?
>>
>> Thanks,
>> - BettyAnn
>>
>>
>> On Wed, 2 Jan 2008 20:11:23 +0000, Bettyann Chodkowski
>> <[log in to unmask]> wrote:
>>
>>> 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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