Hi Rosalia,
That should be ok; although if you are looking at sub-cortical regions
you should use something like FIRST or MIST for segmentation.
Paul
On 21/07/2019, Rosalia Dacosta Aguayo <[log in to unmask]> wrote:
> Hi Paul,
>
> It would be fine then to calculate, for example, the GM volume of, for
> example, the thalamus, for every subject in native space and then divide
> this volume for not-normalized TBV from SIENAX? So, at least, I am
> adjusting for the TBV of every individual, and then run statistics with R?
> Is this accurate form a methodological point of view?
>
> Regards,
> Rosalia
>
> On Sun, Jul 21, 2019 at 2:05 PM paul mccarthy <[log in to unmask]>
> wrote:
>
>> Hi Rosalia,
>>
>> If you are interested in the *absolute* difference in GM volume, then
>> sure - you can calculate this for each subject from the native-space
>> GM PVE map output by FAST.
>>
>> But what is arguably of more interest (and what is tested when you use
>> VBM) are differences in GM volume after it has been normalised by
>> total brain volume. In this way you are just testing GM volume,
>> without being confounded by total brain volume.
>>
>> Cheers,
>>
>> Paul
>>
>> On 20/07/2019, Rosalia Dacosta Aguayo <[log in to unmask]> wrote:
>> > Dear FSL experts,
>> >
>> > As I understand FSL and SPM handle differently Voxel Based Morphometry
>> > analysis. In the case of FSL, if there is an interest in looking at
>> > differences between groups, would it be better to take the volume of
>> > this
>> > area in native space for every individual with fslstats and then make
>> > the
>> > statistics with R, for example?
>> >
>> > Would be this procedure be acceptable? Just because if I normalize the
>> grey
>> > matter into MNI space and the mask as well, then I will miss the
>> > differences in volume.
>> >
>> > I would be very grateful if you could advise me here.
>> >
>> > Best regards,
>> > Rosalia
>> >
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