The Active Cannula

Active Cannulas are a new class of thin, dexterous continuum robots with the potential to reduce the invasiveness of existing surgical procedures, and to access "inoperable" disease. They are designed to traverse narrow and winding environments without relying on “guiding” environmental reaction forces. Active cannulas are particularly well-suited for surgical procedures that require  passage through narrow openings to access air-filled cavities, such as those of the throat and lung.

An active cannula is composed of telescoping concentric precurved superelastic tubes that can be axially translated and rotated at the base relative to one another. Active cannulas derive bending not from tendon wires or other external mechanisms, but from elastic tube interaction in the backbone itself, permitting high dexterity and small size, and dexterity improves with miniaturization. 


A prototype active cannula consisting of three nitinol tubes. Inset line drawing shows degrees of freedom.


We are currently studying active cannula shape and motion to enable physicians to control the device. We  have successfully applied beam mechanics to obtain a kinematic model of active cannula shape, and have developed a number of design tools and procedures. We are currently refining the kinematic model and pursuing visual servoing experiments.

Journal Publications:

  1. D. C. Rucker, R. J. Webster III, G. S. Chirikjian, and N. J. Cowan. Equilibrium Conformations of Concentric-Tube Continuum Robots. International Journal of Robotics Research, 2009. In Review.

  2. R. J. Webster III and N. J. Cowan. Differential Kinematics of Transmissionally Compliant Concentric-Tube Continuum Robots. IEEE Transactions on Robotics, 2009. In Review.

  3. D. C. Rucker, J. M. Croom, and R. J. Webster III. Aiming Surgical Lasers With an Active Cannula. ASME Journal of Medical Devices, 2009. Accepted.

  4. D. C. Rucker and R. J. Webster III. Parsimonious Evaluation of Concentric-Tube Continuum Robot Equilibrium Conformation. IEEE Transactions on Biomedical Engineering Letters, 2009. Accepted.

  5. R. J. Webster III, J. M. Romano, and N. J. Cowan.   Mechanics of Precurved-Tube Continuum Robots.  IEEE Transactions on Robotics, 25(1), 67-78, 2009.

Dissertations:

  1. R. J. Webster III.  Design and Mechanics of Continuum Robots for Surgery.  Ph.D. Thesis, Department of Mechanical engineering, Johns Hopkins University, Baltimore, MD, December 2007.

Patents:

  1. R. J. Webster III, A. M. Okamura and N. J. Cowan, and R. H. Taylor. An Active Cannula for Bio-Sensing and Surgical Intervention. US and International Patents Pending.

Book Chapters:

  1. R. J. Webster III, J. P. Swenson, J. M. Romano, and N. J. Cowan. Closed-Form Differential Kinematics for
    Concentric-Tube Continuum Robots with Application to Visual Servoing.     11th International Symposium on Experimental Robotics 2008, Springer Tracts in Advanced Robotics.  In Press.

Conference Publications:

  1. D. C. Rucker and R. J. Webster III.  Mechanics of Bending, Torsion, and Variable Precurvature in Multi-Tube Active Cannulas. IEEE International Conference on Robotics and Automation, 2009.

  2. D. C. Rucker and R. J. Webster III.  Mechanics-Based Modeling of Bending and Torsion in Active Cannulas. IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics, 704-709, 2008.

  3. R. J. Webster III, J. M. Romano, and N. J. Cowan.  Kinematics and Calibration of Active Cannulas.  IEEE International Conference on Robotics and Automation, 3888-3895, 2008.

  4. 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), 2857-2863, 2006. Finalist: Best Paper Award.

Posters:

  1. D. C. Rucker, J. M. Croom, and R. J. Webster III. Aiming Surgical Lasers With an Active Cannula. ASME Design of Medical Devices Conference, 2009.

  2. J. P. Swensen, R. J. Webster III, and N. J. Cowan.  Active Cannula: Applications to Steerable Needles.  Medical Image Computing and Computer-Assisted Intervention, 2008.

  3. D. C. Rucker, N. J. Cowan, G. S. Chirikjian, and R. J. Webster III.  Toward a General Active Cannula Model. Medical Image Computing and Computer-Assisted Intervention, 2008.