Thirty six deep focal hepatic lesions were induced in eleven piglets by means of an Nd-YAG laser. Laser shots of 80 W power and 10 s duration were used, the beam being transmitted through an echoguided stereotaxic handpiece. From day 0 to day 120, the animals underwent ultrasonographic and morphological controls. At lasering time an hyperechoic image—12–18 mm in diameter—appeared due to boiling of tissue water. During the twenty postoperative days the lesion core was an echo-free area due to tissue vaporization, surrounded by an hyperechoic ring of increasing fibrosis, containing neovascularization and biliary ductules, while the hypoechoic outer area represented the peripheral halo of edema. In the long term, hyperechoic structures—swollen fibrotic septa of homogeneous fibrotic network—invaded the lesion site confirming good healing.
