MRI Abdominal Fat Quantification - Threshold Method

Hi! I am currently working on a clinical project about diabetes remission. I am new to this app and forum, but I encountered some difficulty when I was using the threshold method to quantify fat. We have our MRI images saved as DICOM files, and we are looking to quantify total abdominal fat. How would we determine the threshold value when we create this particular segment? Is it try and error, and is the threshold value unique to each MRI image even if we set the same parameters? Thanks!