Dear Maria Boge Lauvsnes,

We have the similar results with elderly subjects (healthy controls, mci and ad patients). Images are recorded with a 1.5T MRI scanner. We also used the VBM8 default settings. We did the VBM8 processing with our own template, but this had no effect on the results. GM volume is always smaller than WM volume. Visual inspection of the segmentation results show no abnormalities.
In the next step we tried FSL for volume calculation and the results are nearly the same: GM volume is always smaller than WM.

Best regards,

Iven Fellhauer

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Von: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] Im Auftrag von Lauvsnes, Maria Boge
Gesendet: Donnerstag, 13. Juni 2013 09:30
An: [log in to unmask]
Betreff: [SPM] segmentation with VBM8 default settings

Dear SPM experts
I am doing volumetric analyses of a group of 60 patients with autoimmune disease and 60 healthy control subjects. We have MRI images from a 1.5 T MRI scanner, using the axial T1 3-dimensional TFE with 1.6 mm slice thickness. We did the preprocessing with VBM8 tool with default settings, and calculated raw volumes from the *_seg8.txt-files. The resulting volumes was a bit surprising, with WM and GM almost similar, and actually a bit more WM than GM in the group of healthy subjects (mean age of the groups are 55 years). The same images was previously preprocessed with SPM5, and then the GM volume was found almost 100 ml larger, and WM volume more than 100 ml smaller, the sum of WM and GM being almost the same. Do anyone have the same experience? Should I change the settings, for instance of the bias correction? Grateful for any advises.

Best Regards 

Maria Boge Lauvsnes
PhD fellow, Stavanger, Norway