Dear experts,
I am in trouble with two ways of computing mean intensity with mri_segstats.
First I have used on .annot files with three different labels inside (SegId 1 to 3) :
*mri_segstats --annot fsaverage lh cache.th23.pos.sig.ocn.annot --i lh.PET.fsaverage.sm10.mgh --sum lh.pet.sum*
which give me those results: # ColHeaders Index SegId NVertices Area_mm2 StructName Mean StdDev Min Max Range 1 1 27805 14182.6 cluster-001 8.8194 1.4351 6.2105 14.2947 8.0842 2 2 2321 1047.3 cluster-002 10.3661 1.0848 8.8375 12.9317 4.0942 3 3 552 313.1 cluster3 10.3365 0.4711 9.3719 11.8694 2.4975
Second I have created on .label files containing the three segmented labels (SegId 1 to 3) and used this label with mri_segstats:
*mri_segstats --slabel fsaverage lh lh.th23.cluster.thresh1.3.label --i lh.PET.fsaverage.sm10.mgh --excludeid 0 --sum lh.pet.label.sum *
which give me those results: *# ColHeaders Index SegId NVertices Area_mm2 StructName Mean StdDev Min Max Range * * 1 1 30678 15542.9 Seg0001 8.9637 1.4701 6.2105 14.2947 8.0842 *
I verified if I obtained the same results with the two ways (.annot or .label) and everything is fine comparing NVertices, Area_mm2 but Mean in first way gives me (8.8194+10.3661+10.3365)/3 = 9.84066 and with .label file Mean = 8.9637.
Did I have miss anything and how is computed mean intensity ?
Many thanks in advance.
Best regards, Matthieu