Dear Vaishnavi,
to extract data from your images, you could use
spm_sample_vol (takes a list of coordinates in VOXEL space)
spm_bsplinc/spm_bsplins for b-spline interpolation of images
spm_read_vols (reads in whole images - not very efficient if you want to
extract a small number of points)
Differences you observe may be due to different interpolation methods, or
- if you refer to time series going into statistics - different filtering
or image scaling. If you want to extract statistics time series, you may
want to have a look at spm_graph or spm_regions to see how they are
extracted.
Hope this helps,
Volkmar
On Thu, 30 Nov 2006, vaishnavi balasubramanya wrote:
> I have been having a bit of trouble with data extraction from raw images,
> and I was hoping someone would be able to help me. I created a program that
> extracts data in the form of a matrix from the realigned and normalized spm
> images. I have tested a single voxel extraction and compared my results
> with MarsBar, and the results are very different. I think that the problem
> is that I am unsure how the matrix information from the image files is
> transformed into stereotactic space in SPM. Could you provide an
> explanation for what, if any, transformation takes place to make that
> conversion?
>
> Thank you.
> Vaishnavi Balasubramanya
>
>
--
Volkmar Glauche
-
Department of Neurology [log in to unmask]
Universitaetsklinikum Freiburg Phone 49(0)761-270-5331
Breisacher Str. 64 Fax 49(0)761-270-5416
79106 Freiburg http://fbi.uniklinik-freiburg.de/
|