Initially, a set of focus points are identified that were used in {HEAD ~ the scan} of {TAIL ~ a virtual slide image} 
of
Initially , a set of focus points are identified that were used in { HEAD ~ the scan } of { TAIL ~ a virtual slide image }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL