Design and Control of a Magnetic Laser Scanner for Endoscopic Microsurgeries

State-of-the-art surgical laser systems achieve high-quality tissue ablations with minimal thermal damage to the tissue by providing high-speed laser scanning. However, current technology is not applicable to difficult-to-reach anatomical sites for endoscopic surgery. In these cases, flexible laser fibers are used, but the resulting ablation quality is limited. Therefore, there is a need to improve flexible laser surgery systems. This paper proposes a solution to this issue based on a compact laser scanner and a focusing module designed to be placed at the distal end of a flexible endoscopic system. The device uses magnetic actuation to bend a laser fiber; thus, allowing precise 2-D position control and high-speed scanning of a high-power surgical laser. The design, implementation, and control of such a system are described in this paper, with special focus on its dynamic modeling and controller design to provide real-time control and fast automated execution of surgeon-defined trajectories. Validation experiments performed with different trajectories and scanning frequencies attest the performance of the system, which demonstrates trajectory tracing with 90 mu m (1.4 mrad) accuracy for scanning frequencies up to 15 Hz. This is a significant result that promises to bring the benefits of free-beam laser scanning systems to endoscopic microsurgeries.