Hello fellow SPM'ers,
This might be slightly on the side of the common subjects discussed on
the list, but I'll give it a shot anyways.
I am currently collecting data using a 3T Philips Achieva scanner that
unfortunately is plagued (as most other scanners, I've gathered) with
significant drop-out in orbitofrontal areas. I am planning to perform a
DCM model which includes parts of the orbitofrontal cortex as a VOI. I
suppose the standard approach to this would be to use the pickatlas,
IBASPM or something similar to establish a ROI and then extract the time
series. However, there is significant intraindividual variability with
regards to the degree of drop-out in the OFC, and I want to take this
into account when specifying my individual models. This is because I
assume the time series will be corrupted if they include areas of the
OFC have dropped- out, which will mess up my DCM model.
Therefore my question: Is there some established protocol or program
that will allow me to map and mask the suceptibility artifacts, so that
I may tailor my VOI's to each individual, thus maximizing the
probability of detecting relevant activation? The only alternative I can
think of is the labour intensive approach in which I trace the artifact
manually for each of my 40 subjects, and make sure my VOI doesn't
overlap with the artifact.
Any help, comments, pointers?
Best,
Haakon G. Engen
Stud. Psychol., Research assistant
University of Oslo
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