What worries me more than the strange way the CoG is computed though is the fact that the qform is totally ignored. And it doesn't seem to be retrievable in any other way. In spm_vol, nifti() is used to get the .mat information, so no qform there either. Alle Meije Alle Meije Wink wrote: > Nope - from a C perspective it would be +2! > > Alle Meije > > Matthew Brett wrote: >> Hi, >> >> Is it possible you are looking at the +1 necessary to change from 0 >> based to 1 based indexing into arrays (C vs matlab)? >> >> Matthew