Use a "grey matter threshold" to create a mask when you do the analysis.
I would suggest an absolute threshold of about 0.05
Best regards,
-John
-----Original Message-----
From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]
On Behalf Of Remya Nair
Sent: Thursday, May 31, 2007 6:11 PM
To: [log in to unmask]
Subject: [SPM] change spm mask.img
Dear All,
I have been wrestling with this issue for quite some time now mainly due
to
my lack of experience with spm, so I was hoping to find some help here.
I
have perforemd a vbm analysis using spm5 on my data and on viewing the
results I see some outside brain activation that I want to mask out. On
reading through the list, one of the suggestions I found is to modify
the
mask.img to get what I want. Whe I view my mask.img , I see brain stem
regions that are included in the mask(and hence in the stats) that I am
not
interested in. Is there a way I can change the mask(like forcing those
regions to 0) so that it no longer includes this region?
Once this is done I was hoping to use the image as an explicit mask and
rerun the analysis. Would this help me achieve my objective or am I
completely off track here?
Looking forward to suggestions.
Thanks a ton!
RN
|