Deep localized neodymium (Nd)‐YAG laser photocoagulation in liver using a new water cooled and echoguided handpiece

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Abstract
Thirty-six deep hepatic lesions of localized photocoagulation were induced in 11 pigs by means of a neodymium-YAG laser. Laser applications of 80 W/10 sec (10.190 W/cm2) were transmitted through a handpiece coupled to a water-cooling circulation system to protect the quartz fiber and positioned through an echo-guided trocar. During irradiation, temperature was sufficient for vaporization up to 5 mm from the laser source and high enough for tumor cell kill at a 10-mm distance (54°C/60 sec). Intraoperative ultrasound visualized increasing photocoagulation (12–18 mm), and further controls demonstrated an echo-free core of vaporization progressively covered by increasing fibrosis, well demarcated from normal parenchyma. Microscopy revealed central coagulative necrosis marginated from the third day by a growing fibrosis. By day 20 immunoblasts and mast cells were in profusion in the lesion border, and by day 120 a fibrotic network had invaded the scar and confirmed healing free of complication. This technique is proposed for deep vaporization of disseminated hepatic metastases.