FOD amplitude

Hi Mrtrix3 Community,

I have a question regarding how to use seed_cutoff option in tckgen command. I would like to use FA threshold to determine where to initiate tracking seeds. If so, could I use iFOD2 algorithm with an input of FOD image?
Also, in case I’d like to use FOD amplitude for seed_cutoff option, how could I calculate average FOD?

Thank you very much,
Jane