{{{Usage: mri_mask [options] <in vol> <mask vol> <out vol>
This program applies a mask volume (typically skull stripped).
Options:
-xform %s ->apply LTA transform to align mask to input volume
-invert ->reversely apply -xform
-lta_src %s ->source volume for -xform (if not available from the xform file)
-lta_dst %s ->target volume for -xform (if not available from the xform file)
-T # ->threshold mask volume at # (i.e., all values <= T is considered as zero) }}}