you should also plot them on the same axes (or at the very least with the
same limits)
On Fri, 17 Apr 2015, Martin Reuter wrote:
Hi Pradeep,
is this the result of a single subject? In a single subject lot's of things
can happen (e.g. motion artefacts can affect a single time point, other
imaging or measurement noise will have effects). Also how far are the time
points apart? Run the same thing with 20 subjects and you should see
significantly reduced variablility in the longitudinal stream vs the cross
sectional one.
Best, Martin
On 04/16/2015 01:12 PM, Pradeep wrote:
Hello All,
I have pre-processed a subject that has T1 scans at 3 time points
using the freesurfer cross-sectional and longitudinal methods. The
results show a lot of variability. I have attached the plots. Any
advice would be much appreciated.
Thanks,
Pradeep
On Wed, Apr 15, 2015 at 5:26 PM, Pradeep <tprad...@gmail.com> wrote:
Hello All,
I have pre-processed a subject that has T1 scans at 3 time using
the freesurfer cross-sectional and longitudinal methods. The
results show a lot of variability. I have attached the plots.
Any advice would be much appreciated.
Thanks,
Pradeep
On Wed, Jun 4, 2014 at 12:03 PM, Alexandru Hanganu
<al.hang...@yahoo.ca> wrote:
Thank you very much for your answer Bruce !
have a nice evening,
Alex.
Le 3 juin 14 7:6, Bruce Fischl a écrit :
> Hi Alex
>
> I would think that longitudinal analysis is still
the way to go as we try
> to improve both reliability and sensitivity using
the fact that we have
> multiple scans/subject.
>
> cheers
> Bruce
> On Tue, 3 Jun 2014, Alexandru Hanganu wrote:
>
>> Hello Everyone,
>>
>> could someone please give us an advice about
which method you consider is
>> the best for our study ?
>>
>> we have two groups with MRI at Time 1. Each group
received medication. After
>> this we performed another MRI at Time 2 after 2
weeks.
>>
>> The best method for this study is a longitudinal
one or a cross-sectional
>> GLM ?
>>
>> We consider that the distance between the time
points is too small, and the
>> longitudinal method is not the best choice.
Hence, this study should be
>> treated as a cross-sectional one. In this case we
think about performing a
>> simple GLM with the contrasts:
>> 0.5 0.5 0.5 0.5
>> or 1 -1 -1 1
>>
>> for the groups:
>> 1) grp 1 time 1
>> 2) grp 1 time 2
>> 3) grp 2 time 1
>> 4) grp 2 time 2
>>
>> we are searching to see whether medication had
any impact on the cortical
>> morphology in each group and between the groups.
>>
>> Thank you !
>> Best regards,
>> Alex.
>>
>>
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