Figure 1:

Photomicrographs of porcine liver tissue 24 hours after treatment (with 415 mW). * = position of the laser fiber on each image. A, On the H-E–stained section (original magnification, ×10), the treated region is clearly visible as a zone of CN (CN) surrounding the laser fiber. This is surrounded by a more peripheral concentric zone defined by parenchymal necrosis and hemorrhage (HZ). Within this zone, structures such as arteries, veins, and bile ducts are variably affected. A normal-appearing region (NL) is sharply delineated outside the treatment area (indicated by the dotted line). B, TUNEL-stained section (original magnification, ×10) shows a dense, well-circumscribed region of necrotic cells with fragmented DNA (tun+) homogeneously surrounding the laser fiber. C, Photomicrograph obtained after treatment (original magnification, ×40) shows that no changes in the structure of collagen were visible at light microscopy, despite complete ablation and necrosis of surrounding hepatocytes in the CN zone. D, High-power view of an H-E–stained section (original magnification, ×400) from the normal-appearing area shows the normal cellular and architectural appearance of a porcine portal triad, consisting of a bile duct (b), artery (a), and vein (v). E, High-power view of an H-E–stained section (original magnification, ×400) from the CN zone shows complete parenchymal necrosis and necrosis of a small 40-μm vein (v, arrow) and bile duct (b).