3dFWHMx and 3dBlurToFWHM

Dear AFNI Colleagues,

I need to smooth multiple data sets to the same level of smoothness that I estimate using 3dFWHMx . I apply the smoothing with 3dBlurToFWHM and provide the input dataset for -blurmaster and -detrend, which is fine for datasets with more than one time frame.

However, in the cases where only one frame is available, 3dFWHMx has -2difMAD to provide an estimate of smoothness, but I don’t know what to use for -blurmaster with 3dBlurToFWHM since detrending is no longer valid. Is there a way to output the detrended volume created by 3dFWHMx so that i can provide it to 3dBlurToFWHM regardless of whether -2difMAD was used or not? Alternately, is there a command I can use to detrend a la -2difMAD from the command line?

All the best,