Dear Linda, The ‘.f’ “function" gives you the free water volume fractions. So if you want to exclude FA values of voxels with high free water volume fractions, let's say voxels containing more than 70% of free water volume fraction, you have to run the lines of code that you mentioned on your previous email: F = fwdtifit.f FA = fwdtifit.fa FA[F > 0.7] = 0 In the same way, if you want to remove the AD, RD, and MD values on these voxels containing high free water volume fractions, you have to use the following lines of code: MD = fwdtifit.md MD[F > 0.7] = 0 RD = fwdtifit.rd RD[F > 0.7] = 0 AD = fwdtifit.ad AD[F > 0.7] = 0 Note that these later lines of code are different to what you sent before. Best regards, Rafael NH