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Design and kinematic analysis of a neurosurgical spring-based continuum robot using SMA spring actuators

Brain tumor, be it primary or metastatic, is usually life threatening for a person at any age. The risks involved in carrying out surgery within a brain can cause severe anxiety in patients. However, primary surgical resection which is one of the most effective ways of treating brain tumors can have a tremendously increased success rate if the appropriate imaging modality is used for complete tumor resection. Magnetic resonance imaging (MRI) is the imaging modality of choice for brain tumor imaging because of its excellent soft-tissue contrast. MRI combined with continuum soft robotics has immense potential to be the next major technological breakthrough in the field of brain cancer diagnosis and therapy. In this work, we present the design and kinematic analysis of a flexible spring-based minimally invasive neurosurgical intracranial robot (MINIR-II). It is comprised of an inter-connected inner spring and an outer spring to enable motion in three dimensions (3D). Our design provides improved dexterity with higher degrees of freedom (DoFs) and independent joint control because of the centrally routed tendon configuration. Since the robot itself is made of plastic (except the electrocautery probes and SMA spring actuators), it is MRI-compatible and allows surgeons to track the real-time location of the robot in the brain and to reach the brain tumor target. The inter-connected spring and the outer spring are manufactured individually in a single piece using rapid prototyping technology at low cost to make it disposable after single use. Our three-segment robot has two DoFs at each segment with both joints controlled by two pairs of MRI-compatible SMA spring actuators. We also present a detailed kinematic analysis of the robot, simulation of the robot motion, and experimental evaluation of the robot motion using vision feedback.