On Fri, Sep 28, 2012 at 4:02 AM, Martin Reuter <mreuter@nmr.mgh.harvard.edu> wrote:

Hi Shannon,

that cannot be. It either indicates a serious bug (which we have not yet
encountered in our data) or a problem with your processing.

Can you send me:
- the version you use
- the command line you run
- the output you get

Also long_mris_slopes is designed for analyzing surface maps (analysis
on a vertex by vertex basis). This is usually thickness. So I don't
understand what 'volumes' you mean? For an ROI analysis based on stats
files you need to use long_stats_slopes.

Best, Martin

On Thu, 2012-09-27 at 11:37 -1000, Shannon Kogachi wrote:
> Hi Martin,
> Each subject has 3-6 timepoints. They are all about one year apart.
> Here's an example of the discrepancy: one subject with 5 timepoints
> had volumes that ranged from 2.2-2.4. However, from the
> long_mris_slopes command, the temporal average volume was calculated
> to be 1.67. Thanks for your help!
>
> -Shannon K.
>
> On Thu, Sep 27, 2012 at 6:21 AM, Martin Reuter
> <mreuter@nmr.mgh.harvard.edu> wrote:
> Hi Shannon,
>
> long_mris_slopes works for surface maps (both thickness and
> volume
> should work). In both cases it should compute the temporal
> average.
>
> I have another scripts that works for stats files
> (long_stats_slopes) in
> the same way.
>
> How many time points do you have, how far apart (equally
> spaced?).
>
> Best, Martin
>
> On Wed, 2012-09-26 at 14:59 -1000, Shannon Kogachi wrote:
> > Hi Martin,
> > When I used the long_mris_slopes command for the
> thickness, the
> > average thickness calculated in FreeSurfer was pretty
> similar to
> > averaging the values in FreeSurfer. Does this command only
> work
> > thickness measures and not for volume or area? Thanks!
> >
> > -Shannon
> >
> > On Wed, Sep 26, 2012 at 2:49 PM, Martin Reuter
> > <mreuter@nmr.mgh.harvard.edu> wrote:
> > Hi Shannon
> >
> > You probably mean average thickness.
> > My scripts compute the temporal average from the
> linear fit
> > (at mid time), which can be differed from simply
> averaging
> > values.
> > Best Martin
> >
> > Shannon Kogachi <skogachi@gmail.com> wrote:
> > Hi,
> > I had a question about how the temporal
> average is
> > calculated for subjects with multiple
> timepoints. I
> > used the long_mris_slopes command on a
> longitudinal
> > set of data. However, when I compared the
> average
> > volumes calculated through this command to
> the average
> > volumes calculated in excel after extracting
> the same
> > vertices at the individual timepoints, these
> values
> > did not match up. The average volumes
> calculated
> > through long_mris_slopes were smaller.
> Please let me
> > know if there is a way to explain this
> discrepancy.
> > Thank you!
> >
> > -Shannon K.
> >
> >
> >
>
> >
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