Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help bis2fieldtrip”.

  BIS2FIELDTRIP reads BioImage Suite .mgrid files and converts them 
  into a FieldTrip-compatible elec datatype structure and converts electrode
  positions from BioImage Suite mgrid that are in 'xyz' to head coordinates
  of the corresponding MRI volume 
 
  Use as
    elec = bis2fieldtrip('Subject_grid.mgrid', 'Subject_MR.nii')
 
  See also FIELDTRIP2BIS, FT_READ_SENS, READ_BIOIMAGE_MGRID