Optical-fiber-type Contact Force Detector for Improving Safety and Workability of Myocardial Biopsy

In a myocardial biopsy, the physician inserts the myocardial biopsy forceps into the heart chamber with fluoroscopic guidance and operates the forceps to collect the myocardium. The tip of the forceps has a gripper and a two-degree-of-freedom passive joint. The myocardial wall is difficult to see through a fluoroscopic image, and sampling may be missed due to the weak contact force and the large angle between the forceps and the myocardium. To solve these problems, we propose a contact force and bending angle detection mechanism for the forceps using optical fibers. The proposed mechanism has three built-in optical fibers and is connected to light-intensity-modulation-type optical sensors. Before contact, the light of the fibers leaks outside through the forceps shaft gap. When the forceps tip comes into contact with the myocardial wall, the external force reduces the shaft gap and the leak light amount. The physician can detect the contact force and bending state at the tip from the ratio of the three measured values. We evaluated the proposed mechanism in in vitro and in vivo experiments. We confirmed that the contact force under 1.4 N and bending angle over 30 deg can be detected.