{HEAD ~ These focus points} are used to determine {TAIL ~ a best fit surface} for the virtual slide image 
are used to determine
{ HEAD ~ These focus points } are used to determine { TAIL ~ a best fit surface } for the virtual slide image
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH