Hi Stephen,
> I am starting to analyse some fMRI data using SPM5, and came across the
> parameters "Quality" and "Separation" when realigning my images. I was
> wondering how great the benefit would be if I changed these parameters
> from the current default values? (i.e., making Quality = 1, and Separation
> = 1 or 2mm)?
Well, the quality parameter has already been upped from spm2 to the spm5
defaults, so this could be something worth looking into, although
processing time will increase. As to the separation, I do not think it
makes too much sense to set it to these minimal values for fMRI data as
you will get be within the same voxel if you don't have hi-res data.
There is, if I remember correctly, a certain amount of random variation
introduced in setting the points so that the algorithm doesn't get
caught on edges, so setting it to your base resolution probably makes
sense. You could actually find it out it if you construct a time series
with known motion and try out the different settings.
Best,
Marko
--
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Marko Wilke (Dr.med./M.D.)
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Universitäts-Kinderklinik University Children's Hospital
Abt. III (Neuropädiatrie) Dept. III (Pediatric neurology)
Hoppe-Seyler-Str. 1, D - 72076 Tübingen
Tel.: (+49) 07071 29-83416 Fax: (+49) 07071 29-5473
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