Hello Noelia,

the units can be µL, if you use modulated data.

So, a value of 1 in a voxel of 1x1x1 mm3 represents 1 µL.

A value of 1 in a voxel of 2x2x2 mm3 would represent 8 µL.

A value of 0.5 (just as example) in a voxel of 1.5 x 1.5 x 1.5 mm3 would

represent (1.5)^3*0,5 = 1.6875 µL.

By the Jac. modulation step the original probability information is paired

with the spatial information of expansion/compression process during

the spatial normalisation steps (incl. DARTEL or whatever you used);

by this pairing information probability can be thought of becoming

an interpretable volume.

Bw,

Philipp

Von: SPM (Statistical Parametric Mapping) [[log in to unmask]]" im Auftrag von "Noelia Martinez Molina [[log in to unmask]]
Gesendet: Donnerstag, 13. September 2018 11:38
An: [log in to unmask]
Betreff: [SPM] Grey Matter Volume Units

Dear SPM experts,

I performed a VBM analysis using spatially normalised "modulated" images of grey matter tissue and would appreciate if someone could tell me what are the volume units that I should report (voxels? mm3?). I´m not sure about the transformations applied to the images and how these would affect to the units.

Thank you in advance for considering my post.

Kind regards,
Noelia