Dear SPMers,
a categorical comparison between 2 groups of patients and controls (FDG-
PET; SPM2) produced statistically significant clusters within four
anatomical regions.
I'd like to know metabolism in which anatomical regions allows for the best
discrimination between controls and each of 2 patient groups. For this
purpose, i'm going to extract (individual) regional metabolic values
from the regions and introduce them into a logistic regression analysis.
What is the most rational/valid way to extract regional values?
a) ideally (?) would be to extract values exactly from the clusters
assigned to the definite anatomical regions (e.g. using a VOI tool of
SPM2). But the problem here is that 3 clusters assigned to the anatomically
different regions are merged with each other. I.e. the VOI tool will
extract average values within 3 merged clusters and 1 separate cluster.
c) to extract values from one peak (with maximal t-value) voxel or sphere
of say 10mm within each of 4 clusters again using the VOI tool.
b) to extract average values within the whole anatomical region (from 4
regions), where clusters were detected. Stereotactical VOI masks are
needed, a marsbar tool can be used.
What would you advise?
Many thanks,
Igor
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Igor Yakushev, MD
Department of Nuclear Medicine
Johannes Gutenberg University Mainz
Mainz/Germany
Tel +49/6131/176739
Fax +49/6131/172386
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