Design, development, and evaluation of meso-scale robotic system for deep intracranial tumor removal

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Cheng, Shing Shin
Desai, Jaydev P.
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It remains a challenging procedure to remove deep brain tumor due to its location around critical brain structures, the limitations in existing surgical tools, and the lack of real-time image guidance. The Minimally Invasive Neurosurgical Intracranial Robot (MINIR-II) project aims at combining flexible robotic technology, minimally invasive approach, and magnetic resonance imaging (MRI) to achieve more precise and complete removal of brain tumor. MINIR-II is a spring-based 3-D printed flexible robot that is tendon-driven and equipped with electrocautery, suction and irrigation capabilities. A novel central tendon routing mechanism has been employed to enable independent segment control in a tight workspace. To improve stability of the surgical procedure, a stiffness tunable MINIR-II with shape memory alloy (SMA) spring segments has also been developed and characterized to investigate the effect of tendon locking and SMA segment stiffening on the stiffness of individual segment. SMA springs have also been used as a proof of-concept MRI-compatible actuator for MINIR-II. To improve the actuation bandwidth, cooling module-integrated SMA springs have been developed together with a new actuation mechanism involving the alternate passage of water and compressed air. A phenomenological model and a heat transfer model were developed and verified to model the actuator behavior in antagonistic configuration. With the robot developed and tested for its performance and MRI-compatibility, ultrasonic motors were used instead of SMA springs to provide a more reliable actuation solution. A remote actuation strategy with three different transmission designs was implemented due to the interference of ultrasonic motors and drivers with the MR image quality when they are in close proximity to the MR isocenter. The inefficiency in force transmission in the first flexible Bowden cable transmission led to the development of the second rigid transmission as well as the third improved version of the rigid transmission. The robotic system was finally evaluated in terms of its workspace, segment coupling effectiveness, precision, repeatability, and hysteresis behavior. A compact MRI compatible robotic system used to actuate a multi-DoF skull-mounted flexible robot has been presented. Research innovation could be found in the 3-D printed flexible robot design, compact SMA spring cooling module development, stiffness modulated robot design, and transmission design in the MR environment. Intrinsic sensor integration and more user-friendly control interface are two important future works that would take the robotic system one step closer to being clinically evaluated.
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