I would like to apply white matter mask (wm.mgz) produced by freesurfer recon-all command on FLAIR. The FLAIR and wm.mgz have different dimensions such that Flair is 512by512 while wm.mgz has 256by256 in dimensions. I tried to fix this by resizing the flair in matlab but after applying the mask the result is not good. I don't get the difference in dimension anymore though. 

Is there any way that I can resize a mgz volume in freesurfer? 

Many thanks,

Arash