Dear SPM community,
I have decided to repost my questions since I have received no answer, and
have actually received queries from others interested to know the answer
(I'm not alone)...
I think that this is a fairly important capability, and have seen studies
that reported results of %rCBF or %change calculated from a small region.
How can I do that in SPM99? I have only been able to calculate %change in a
single voxel or the full "eigen time-series" in a V.O.I., but have no idea
how to get the % signal change (a scalar) in a VOI without going voxel by
voxel or regressing the time series with my box-car design...
What am I missing?
Shy
> Dear SPM gurus,
> I was able to find in previous postings explanation of how to claculate
the (mean brain normalized) percent
> change in a certain voxel (using plot -> contrast of parameter estimates),
and how to obtain the time series > of changes in a volume of interest
(using the new spm_regions function). I was wondering if you could assist >
me with the following two questions:
>
> 1. How can one obtain the percent change estimate for a small V.O.I., i.e.
a single number rather than the
> full time series? I'm getting too much variance when looking at the
percent change in a single voxel, and I > think that for instance, the mean
beta values in a VOI would be a better representative.
> 2. Is there a simple way of finding the location of (global and/or local)
maximal signal change, rather than > the location where the t statistic is
maximised?
> thanks in advance,
>
Shy
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