Superelastic Surgical Robots
Figure 1: Steerable Needles harness the bending effect of the wedge-shaped bevel tip to steer through tissue.
Figure 2: Active Cannulas are mm-scale curved robot arms that dexterously reach confined surgical sites.
Figure 3: Curved elastic tubes force each other to bend to reach equilibrium as they are rotated axially and extended.
By designing very small robots using superelastic elements, we are extending the reach of surgeons into very small and confined locations in the human body. Toward this goal, we are currently pursuing two distinct projects: Steerable Needles and Active Cannulas.
Steerable needles are much like normal needles except that they are made from superelastic nitinol, which is very flexible. This flexibility amplifies the bending effect of the wedge-like bevel tip as the needle is pushed into tissue. By robotically controlling the axial spin of the needle one can control the direction the needle tip will go as it travels through soft tissue. Driving the needle is actually much like driving a car or bicycle: it is a nonholonomic system. Using nonholonomic models, we are currently developing automatic controllers and teleoperation techniques to drive the needle to surgical targets using feedback from medical imaging systems. This work is in collaboration with Noah Cowan and Greg Chirikjian (JHU) and Ken Goldberg (UC Berkeley).
Active Cannulas are similar to steerable needles, but do not need to be inside soft tissue to steer. They are made from telescoping pre-curved superelastic tubes. Pushing the tubes in and out of each other and rotating them axially creates interesting “snake-like” dexterous motion that can be used to enable surgical interventions deep inside difficult-to-reach areas of the human body. We are developing beam-mechanics based models describing how the tubes cause each other to bend, allowing us to use them as miniature curved robot arms. Using image feedback, we can plan optimal paths for Active Cannulas to reach useful surgical sites. The doctor can then use them to accomplish the surgical objective. This work is in collaboration with Noah Cowan (JHU).
V. Kallem and N. J. Cowan. "Image-guided Control of Flexible Bevel-Tip Needles," IEEE International Conference on Robotics and Automation, 2007, to appear.
R. J. Webster III, A. M. Okamura, and N. J. Cowan. "Toward Active Cannulas: Miniature Snake-Like Surgical Robots", IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2006, pp. 2857-2863.
R. J. Webster III, J. S. Kim, N. J. Cowan, G. S. Chirikjian and A. M. Okamura, "Nonholonomic Modeling of Needle Steering," International Journal of Robotics Research, Vol. 25, No. 5-6, pp. 509-525, May-June 2006.
R. Alterovitz, A. Lim, K. Goldberg, G. S. Chirikjian, and A. M. Okamura, "Steering Flexible Needles Under Markov Motion Uncertainty," IEEE/RSJ International Conference on Intelligent Robots and Systems, 2005, pp. 120-125.
R. Alterovitz, K. Goldberg, and A. M. Okamura, "Planning for Steerable Bevel-Tip Needle Insertion Through 2D Soft Tissue with Obstacles," IEEE International Conference on Robotics and Automation, 2005, pp. 1652-1657.
R. J. Webster III, J. Memisevic and A. M. Okamura, "Design Considerations for Robotic Needle Steering," IEEE International Conference on Robotics and Automation, 2005, pp. 3599-3605.
W. Park, J. S. Kim, Y. Zhou, N. J. Cowan, A. M. Okamura, and G. S. Chirikjian, "Diffusion-Based Motion Planning for a Nonholonomic Flexible Needle Model,'' IEEE International Conference on Robotics and Automation, 2005, pp. 4611-4616.
R. J. Webster III, N.J. Cowan, G. S. Chirikjian, and A. M. Okamura, "Nonholonomic Modeling of Needle Steering." 9th International Symposium on Experimental Robotics, Springer Tracts in Advanced Robotics, Vol. 21, Mar 2006, pp. 35 - 44.