A ring applied to the surface of the tissue stabilizes the tissue to the optics and localizes {HEAD ~ a portion} of the tissue surface through {TAIL ~ an aperture} in the ring 
A ring applied to the surface of the tissue stabilizes the tissue to the optics and localizes { HEAD ~ a portion } of the tissue surface through { TAIL ~ an aperture } in the ring
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH