Thank you so much for your help and these links!
I was able to apply your threshold method on MRhead and then on my MRI. This technique is really easier, thank you.
Concerning the volumes and the “Segment Statistics” table, I understood that (1) (2) and (3) represent different volumes, but according to you, which volume represents better the reality (i.e. the real volume) between Labelmap statistics, scalar volume statistics or closed surface statistics?
A topic has already been opened concerning this question but there is no answer ( Differences between closed surface volume, labelmap volume and scalar volume ).
Thanks