Development of Robot-assisted Ultrasound System for Fetoscopic Tracking in Twin to Twin Transfusion Syndrome Surgery

Twin to Twin Transfusion Syndrome (TTTS) is one of the most severe conditions of congenital anomaly. Fetoscopic Laser Photocoagulation (FLP) has been shown as the preferred treatment for TTTS. The complicated intrauterine environment and limited incision diameter make FLP a very challenging surgery. Besides, the motion of the fetoscope is complex. Ultrasound (US) probe is used to offer a view of the anatomy as well as the relative pose of the fetoscope. However, keeping the fetoscope tip (FT) in view is difficult. A robotic US system could potentially solve the complex US probe handling and could improve the surgeon's view of the intrauterine scene. In this paper, an automatic fetoscope tracking algorithm was developed and ensured safe interactions between robot and fragile tissues for FLP surgery. The US probe attached to the robot was controlled by a hybrid position-force control strategy. For evaluation, four fetoscope motion profiles were investigated on a custom-designed phantom. The system achieved a 78.87% visibility rate for the US image evaluation. The contact force was 0.99± 0.68 N during the tracking to ensure the patient's safety. The proposed system demonstrates the capability of accurate real-time fetoscope tracking.