[Brains-users] longitudinal study

[Ronald Pierson]

The main thing that I think is important is to coregister the followup
scans for a subject to their first scan.  That will take out the
variability due to differences in alignment.  Often the anterior or
posterior commisure will be show up slightly differently on different
scans, and if the AC or PC points are picked differently during
realigning and resampling, the brain will not be aligned the same way in
Talairach space.  Since the lobe measures are based on the locations in
Talairach space, the partition of the tissue volumes between the lobes
will not be the same.

To coregister a followup scan to an intake scan we have included the
longitudinal coregistration.  This is to coregister the T1 from a new
scan to the first scan for this subject.  However, this looks for an
intake scan based on how we set up our directory structure here at Iowa.
If you use one of the other options (ACPC or Other) from the alignlinear
toolbar it should be fine, you just need to fill in the image names and
create an .init file like you do for normal alignlinear.  Better yet,
use the mutual information coregistration - I have gotten much more
consistent results with this.

You can likely use the talairach parameters from the intake scan, but we
always check them.  Also. some have suggested using the brain mask from
the intake scan, but we have generally found that there are too many
little changes along the edge that need to be made; it is easier to
start with a fresh ANN brain mask and trim it.

Ron


On Mon, 2006-02-20 at 19:20 +0100, roberto roiz wrote:
> Dear Brains2 users
> We are working on a longitudinal study. We make three different magnetic
> resonances for each patient. 
> I was wondering which is the best way to work on a longitudinal study.
> Can I analyse separately each of the three magnetic resonances or should I
> use some of the transforms and parameters (Talairach and cerebellum
> parameters and Resample Transform) obtained working on the first magnetic
> resonance to analyse the others?. 
> I have notice there is the following option on the Brains2 Toolbar:
>  Workup/RunAir/Longitudinal
> but is is not available on my Toolbar
> 
> Thanks a lot 
> 
> Roberto Roiz
> Hospital Marques de Valdecilla
> Unidad Investigacaión en Psiquiatria
> Santander
> Spain
> 
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-- 
Ronald Pierson <ronald at psychiatry.uiowa.edu>