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That should work. If you want volumes in litres, ml or whatever, then also multiply by the volume of each voxel. I'd suggest not using the resulting volumes for any statistical analysis though - unless you are testing a hypothesis that is orthogonal to the hypothesis used for generating the blobs. Best regards, -John On 2 April 2018 at 18:27, William Donald Hopkins <[log in to unmask]> wrote: > We have run a VBM analysis and identified GM differences between > individuals with different genotypes. We want to characterize the > differences in gray matter volume within each cluster between our groups by > directly comparing GM within each cluster. To do this, we did the > following: > > > 1) Created a binary mask for each cluster > > 2) We multiplied the individual subjects modulated GM volume by the mask > (which was binary) > > 3) We calculated the volume of gray matter within each cluster, and set > the minimum threshold to .10 to remove low intensity/volume voxels > > > Is this correct? > > > Thank you, Bill Hopkins > > > > > > > > > > -- Prof John Ashburner Professor of Imaging Science UCL Institute of Neurology Queen Square Wellcome Trust Centre for Neuroimaging University College London 12 Queen Square, London, WC1N 3BG E: [log in to unmask] T: +44 (0)20 3448 4365 http://www.fil.ion.ucl.ac.uk/