Thanks Mark for the detailed response!
> On Oct 23, 2016, at 1:11 PM, Mark Jenkinson <[log in to unmask]> wrote:
>
> Hi,
>
> I would not worry about this too much as the precision of these estimates is not better than the number of significant figures you get in the scientific notation.
>
> As for comparing volumes, we would definitely recommend correcting for head size in some way. One good way is to use the VSCALING values from SIENAX to normalise the values from FAST, but note that you can also use the GM and WM outputs from SIENAX directly and these are likely to be more accurate than values from FAST, even with normalisation. If you want to compare CSF values then you should be extremely careful about your brain extraction as the CSF volume is very, very sensitive to this and because the brain extraction is not normally very accurate we do not recommend comparing CSF values that include outer CSF. If you restrict it to ventricular CSF then that is much more accurate and you should also normalise that with VSCALING before comparing values.
>
> All the best,
> Mark
>
>
>
>> On 18 Oct 2016, at 03:02, Dana Wagshal <[log in to unmask]> wrote:
>>
>> Hi FSL group,
>>
>> I'm trying to get white, gray matter, and CSF volumes from T1 data. I ran FAST and am using fslstats to extract the parameters:
>>
>> ex. extract CSF volume for a subject:
>>>> fslstats T1_reorient_brain_pve_0.nii.gz -M -V | awk '{ print $2 * $3 }'
>> 1.6089e+12
>>
>> But when I do this for another subject my value is: 1302770299518
>>
>> I'm worried that when I compare these values between subjects that it won't be as accurate with some numbers in scientific notation and others in number format. Is there a way to have every value display in number format?
>>
>> Best,
>> Dana
>>
>> P.S.- basic question, but will I need to normalize these values in order to compare them (i.e. run SIENAX and multiply the value from fslstats by the VSCALING number)?
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