A small pore size is used and {HEAD ~ the grid} has {TAIL ~ a thickness} chosen to provide high scatter rejection 
A small pore size is used and { HEAD ~ the grid } has { TAIL ~ a thickness } chosen to provide high scatter rejection
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH