Dear SPMers,

I’m dealing with a two-group design with perfusion SPECT. I first created a T-Map and then I extracted the values using a VOI from one region I was interested in (the right OFC). Now I want to find the cerebral areas whose perfusion is correlated with the OFC, using the values extracted from the VOI as covariate (using the method published by Lee et al: Metabolic connectivity by interregional correlation analysis using statistical parametric mapping (SPM) and FDG brain PET; methodological development and patterns of metabolic connectivity in adults. Eur J Nucl Med Mol Imaging. 2008 Sep;35(9):1681-91).

I would like to ‘split’ the covariate column from one (as in the attached design#1) into two distinct columns (as in the attached design#2) to define the contrasts (for example ‘positive correlation OFC in group 1’ and ‘positive correlation OFC in group 2’) because I need to perform and exclusion masking group2 - group1.

 

I am wondering whether this is the right design (I’m not sure mainly about the covariate specifications):

                In a full factorial design I insert one Factor (group) with two levels; then I selected two cells (cell#1= levels: 1, scans: group of patients; cell#2= levels: 2, scans: group of controls); one covariate as vector I inserted all the values obtain from the VOI and then I specified interaction with factor 1 with no centering; relative thresholding masking 0.8; omit global calculation; normalization AnCova.

 

Thanks so much to everyone who would be so kind to help me

 

Roberto