Handheld Micromanipulator for Robot-Assisted Microsurgery

Abstract

Robot-assisted surgery has been increasingly adopted in a wide variety of surgical applications because it offers fine manipulation with high precision and dexterity. Despite the commercial success of robotic platforms, practical use in microsurgery is still challenging due to a considerable level of accuracy required at sub-millimeter scales. Limited visualization and constrained accessibility also hinder operation under operating microscopes. Furthermore, lack of tactile feedback may lead to substantial and even irrecoverable injury. To address these issues in microsurgery, a handheld micromanipulator, Micron, has been introduced as an alternative to conventional robotic platforms. It allows surgeons to directly maneuver surgical tools, while selectively filtering out erroneous motion such as hand tremor. Thus, surgeons can attain the natural feel of manual operation and also direct tactile feedback from the tool attached to Micron. However, the existing Micron still entails several drawbacks in terms of the lack of degrees of freedom, limited range of motion, and ergonomically undesirable design. This thesis presents a new design of the handheld micromanipulator and also explores automated microsurgery in conjunction with image-guidance. For the design of a miniature 6-DOF manipulator, a new optimization framework is introduced, resulting in the optimal dimension of the manipulator given the limited force capability of the miniature actuators used. Given the 6-DOF manipulation, the new platform allows the possibility of imposing a remote center of motion (RCM) for controlling an end-effector, which is generally required in most of minimally invasive surgery. Moreover, the new manipulator attains an order-of-magnitude increase in the range of motion so that it enables automated operations for intraocular OCT scanning and laser photocoagulation. We experimentally verify the design of the 6-DOF Micron and also evaluate its handheld performance under various conditions, which shows significant reduction of hand tremor. In addition, the 6-DOF Micron is utilized to improve the quality of handheld OCT imaging and obtain multi-dimensional structures from single-fiber OCT scanning. The goal of this thesis is to accomplish automated subtasks in microsurgery using the newly developed handheld micromanipulator and image-guidance in realistic environments. Initial work demonstrates the feasibility of automated intraocular laser photocoagulation using position-based visual servoing, while compensating the eye movement. To realize automated surgery in an intact eye, we propose a monocular hybrid visual servoing scheme, incorporating cone beam reconstruction for surface estimation, partitioned visual servoing control, and adaptive frameworks in control. These approaches are validated through experiments with the eye phantom in vitro and porcine eyes ex vivo.