Distance measuring navigation for fetoscopic laser photocoagulation to treat twin-to-twin transfusion syndrome: Feasibility evaluations

This paper reports feasibility evaluations of a distance measuring navigation for fetoscopic laser photocoagulation (FLP) of placental anastmotic communicating vessels between twin fetuses to treat twin-to-twin transfusion syndrome (TTTS) in intrauterine fetal surgery. This navigation uses only a laser fiber for photocoagulation and a fiberscope for a fetoscope, which are usually used in conventional FLP, and a computer to analyzing the fetoscopic view including a laser fiber tip and a guide-spot of red diode-laser. From fiberscopic view, pixels between center of the fetoscopic circular view and center of the guide-spot irradiated from a laser fiber are automatically detected. These pixels can be converted to the real distance between fetoscope tip and target according to geometric and optical relation of a laser fiber and a fetoscope including warping correction. In distance measuring evaluation, measuring errors between the fiberscope tip and target plates were under ±1 mm around 10-mm distance from the target regardless of target angles (0-40 degrees) and colors. In conclusion, accuracy of our distance measuring navigation can provide more secure FLP in clinical use with minimum instruments.