Laser irradiation control of fetal endoscopic surgery for twin-twin transfusion syndrome; Verification of blood-flow interception by in vivo experiment

Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi; Chiba, Toshio*

The fetoscopic laser photocoagulation of chorionic plate anastomosing vessels is main treatment for the twin-twin transfusion syndrome. However, in this treatment, it is required highly endoscopic technologies, for example, blood flow measurement, estimation of distance between placental vessels and irradiation fiber tip and so on. We research and develop a composite-type optical fiberscope (2.2 mm in diameter), which has centrally-located cautery laser fiber and surrounding located fiberglasses for viewing. The laser transmitting efficiency of our fiberscope was very high (84.7%), and certain degree of cauterization was performed with from 20 to 40W laser power, when the distance between irradiated area and fiber tip was 10 mm. In addition, we emitted the laser to porcine liver for laser power control using a thermocouple as a basic research for intercepting placental blood flow, and we controlled the temperature of irradiation spot within 0.3C error in previous paper. In this study, we emitted the laser to in vivo porcine mesenteric vessel with blood flow for laser power control under temperature measurement. From the experimental result, the target temperature of 60 and 70C with feedback control system using thermocouple was controlled low power of about 17W maintain target temperature within 2.0C error. Moreover, we measured the blood flow before and after laser irradiation by a laser Doppler blood-flow meter, and confirmed quantitatively the blood flow blocking.