Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_transform_vol”.

  FT_TRANSFORM_VOL applies a homogenous coordinate transformation to
  a structure with an EEG or MEG colume conduction model. The homogenous
  transformation matrix should be limited to a rigid-body translation
  plus rotation and a global rescaling.
 
  Use as
    headmodel = ft_transform_vol(transform, headmodel)
 
  See also FT_READ_VOL, FT_PREPARE_VOL_SENS, FT_COMPUTE_LEADFIELD, FT_TRANSFORM_GEOMETRY