Dear fsl users, I used sienax, siena and voxelwise siena for cross
sectional, longitudinal and statistic analysis between two groups Controls
and Parkinsonians.
From the 8 sets (each set of 2 scans at intervals of 0 and 5 years) of
Controls and after the use of sienax 6 of them showed growth in NBV ( the
5th year’s sienax result had bigger NBV than the 0th year's sienax result)
and only 2 of them showed atrophy. I was expecting to see atrophy in all of
them so I checked if I did a mistake by considering the scans of the 5th
year as the scan of the 0 year but everything was correct. Normally the
scans of 5th year should show less NBV than the 0st year’s scans, Am I
right? What’s your opinion?Why do I have results that shows growth instead
of atrophy?
At the same time the results of siena in all Controls showed growth rates
instead of atrophy!!Why is that? (I used the set up: siena “0 year scan”
“5th year scan” . With the set up siena “5th year scan” “0 year scan” I had
almost the same PBVC as previously but in this case showing atrophy. Which
setup is the right one and why?)
According to S.M Smith et al./neuroimage 36 (2007) 1200-1206 siena and
sienax -especially in NBV and PBVC- exhibit high correlation but why in my
case I have such uncorrelated results ??(in both siena set ups there are
cases where PBVC and NBV give totally opposite information. For instance NBV
shows growth and PBVC atrophy.. Which results should I “trust”??)
As far as it concerns the Patients group from the 13 sets of data 12 of them
showed growth of PBV and only 1 showed atrophy while siena ( with the set
up: siena “0year scan” “5th year scan”) showed growth is 7 cases and atrophy
in 6.
Totally unexpected values for both Controls and Patients. Do you have an
idea on why this happens?
I also run voxelwise siena and found some evidence of atrophy among patients
(compared to the healthy subjects) but since the results of siena –sienax
are bizarre , I can’t rely on the results of randomise, can i? since
randomise uses as input the results of siena then these significant areas of
atrophy among patients are wrong…Am I right?
Correct me if I’m wrong , normally I should expect NBV in Controls to reveal
atrophy between older and new scans , a result that should agree with the
siena results and as far as it concerns patients more atrophy (in both siena
and sienax) should be expected comparing to controls..
I would really appreciate your help
Thanks a lot for your time
Antonios-Constantine Thanellas
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