Hi Bruce,
Thank you for your quick reply!
The decrease in percent difference vary. I have listed the range here for each region:
Left Lateral Ventricle: -26 to -0.06 Left inferior ventricles: -67 to -0.2 Third ventricle: -23 to -0.06 Fourth ventricle: -7 to -0.142 Right lateral ventricle: -21 to -0.04 Right inferior ventricle: -59 to -0.68
I had a chance to examine one brain that showed -16% difference score in the left lateral ventricles between the longitudinal and baseline scan. The scans seemed to show a smaller left lateral ventricle at time 2. Do you know whether the variability of Freesurfer (version 5.1) may contribute to some of the decreases I am seeing?
Thank you in advance for your help.
Best, Tamara
Message: 32 Date: Tue, 5 Sep 2017 21:43:23 -0400 (EDT) From: Bruce Fischl fischl@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] Ventricle Volumes Decreasing over time? To: Freesurfer support list freesurfer@nmr.mgh.harvard.edu Message-ID: alpine.LRH.2.20.1709052142520.4038@gate.nmr.mgh.harvard.edu Content-Type: text/plain; charset=US-ASCII; format=flowed
Hi Tamara
have you visualized the multiple time points of a subject whose ventricular volume is decreasing? How big a decrease are you seeing?
cheers Bruce
On Tue, 5 Sep 2017, Tamara Tavares wrote:
Hello, I used the default longitudinal stream to calculate ventricular volumes
over time. When I examined
the difference score (longitudinal-baseline) I noticed that for some
participants ventricular
volumes decreased. The same site, scanner and scanning protocol was used
for both baseline and
longitudinal scans. I processed the cross, template and longitudinal time
points on the same
computer using the same Freesurfer version (v 5.1). Furthermore, this
decrease in ventricular volume
is evident before and after manual corrects were made to the aseg file.
Is it common to see an
decrease in ventricular volume over time? Can this be due to Freesurfer
variability or slight
differences in the scanner over the two time points?
Thank you in advance for your help.
Best, Tamara
Hi Tamara
but have you looked at the two timepoints in freeview to see if the ventricles are actually decreasing or of it is a segmentation error? Is that what you mean when you say you examined it? If the segmentations look accurate I'm not sure what else we can do. I guess you could try installing 6.0 and rerunning these subjects to see if the results persist. 5.1 is pretty old
cheers Bruce
On Wed, 6 Sep 2017, Tamara Tavares wrote:
Hi Bruce,
Thank you for your quick reply!
The decrease in percent difference vary. I have listed the range here for each region:
Left Lateral Ventricle: -26 to -0.06 Left inferior ventricles: -67 to -0.2 Third ventricle: -23 to -0.06 Fourth ventricle: -7 to -0.142 Right lateral ventricle: -21 to -0.04 Right inferior ventricle: -59 to -0.68
I had a chance to examine one brain that showed -16% difference score in the left lateral ventricles between the longitudinal and baseline scan. The scans seemed to show a smaller left lateral ventricle at time 2. Do you know whether the variability of Freesurfer (version 5.1) may contribute to some of the decreases I am seeing?
Thank you in advance for your help.
Best, Tamara
Message: 32 Date: Tue, 5 Sep 2017 21:43:23 -0400 (EDT) From: Bruce Fischl fischl@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] Ventricle Volumes Decreasing over time? To: Freesurfer support list freesurfer@nmr.mgh.harvard.edu Message-ID: alpine.LRH.2.20.1709052142520.4038@gate.nmr.mgh.harvard.edu Content-Type: text/plain; charset=US-ASCII; format=flowed
Hi Tamara
have you visualized the multiple time points of a subject whose ventricular volume is decreasing? How big a decrease are you seeing?
cheers Bruce
On Tue, 5 Sep 2017, Tamara Tavares wrote:
Hello, I used the default longitudinal stream to calculate ventricular volumes over time. When I examined the difference score (longitudinal-baseline) I noticed that for some participants ventricular volumes decreased. The same site, scanner and scanning protocol was used for both baseline and longitudinal scans. I processed the cross, template and longitudinal time points on the same computer using the same Freesurfer version (v 5.1). Furthermore, this decrease in ventricular
volume
is evident before and after manual corrects were made to the aseg file. Is it common to see an decrease in ventricular volume over time? Can this be due to Freesurfer variability or slight differences in the scanner over the two time points?
Thank you in advance for your help.
Best, Tamara
freesurfer@nmr.mgh.harvard.edu
-
Bruce Fischl -
Tamara Tavares