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I have to agree with Alexander. Your control group has normal cortex, and your patient group has atrophied cortex. Spatial norm of all these brains to a standard template would likely result in the results you have recieved. You can try making your own template from the 40 patients. Coregister them all, and then average them. Spatially normalize that brain using 12-parameter linear affine and the template bounding box. Use this as the basis for spatial norm of all patients and the controls. However, you may have exactly the opposite problem as before...but it's worth a try. Good luck, James Sean Colloby wrote: > > Dear SPM community, > > I am relatively new to the realms of SPM, I would be > extremely grateful if anyone you could help me on a few issues > regarding my analysis. > > Until now I have been using the windows version of SPM to make a > group comparison between 20 controls and 40 Alzheimer patients > (SPECT Tc-HMPAO Images - voxel size 5.40mm). > > I have normalised all images to the PET template, using the 12 > parameter affine transform, MNI bounding box and resliced to the above > voxel size of 5.40mmx5.40mmx5.40mm. The images were then > smoothed to a FWHM of 15mm x 15mm x 15mm. > > For the analysis, I then choose the option of Scaling, with a single > study and single subject containing two conditions. The controls > condition and the AD patients condition. I then set my contrast to > (1, -1) and ran the analysis. > > When I looked at the glass brain data, the only regions of > significance where in the ventricles? Nowhere else, i.e.,in the > frontal, temporal or parietal regions? Not even when I set very > liberal uncorrected p values and number of voxels per cluster to 1. > > Am I doing this analysis correctly? Is it my reslicing, or have I set > up the PET statistics wrongly, or maybe I have very poor data? Surely > there must be some differences! > > Can anybody possibly help me and give me some useful pointers? > > Thanks. > > Sean Colloby > Research Associate > Wolfson Research Centre > Newcastle General Hospital. -- ============================== James C. Patterson II, MD/PhD Clinical Fellow NIMH, Bldg 10, room B1D-65b work: 301-402-1379 pager: 104, 5643 (NIH only) fax: 301-402-1370 Wisdom yields uncertainty. I wish I wasn't sure of that. ============================== %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%