This is for my master thesis. I already tried FSL tool and commands but it did not result!
Hi @Carolina,
You may be better off asking this in an imaging forum – FSL has a vibrant support forum which will most likely have some good advice for you, Support - FslWiki (or JISCMail - FSL List at WWW.JISCMAIL.AC.UK directly). They’ll be best able to help if you offer a little more detail on exactly what steps you have tried and what output (or error message) you see.
FSL FAST sounds like a reasonable choice to me; here is a recent small study which demonstrates this for CT segmentation.