For smoothing volumetrically, you can use
svreg_smooth_vol_function.sh
Please type it on the command line without any arguments to see the usage.
svreg_smooth_vol_function : This script performs 3d vol news
Authored by Anand A. Joshi, Signal and Image Processing Institute
Department of Electrical Engineering, Viterbi School of Engineering, USC
usage: svreg_smooth_vol_function.sh in_file stdx stdy stdz out_file
required input:
in_file: input vol file
stdx,stdy,stdz: std dev (in mm) in 3 directions
out_vol: output vol file