title: Virtual remote center of motion control for needle placement robots.
abstract: OBJECTIVE
  We present an algorithm that enables percutaneous needle-placement procedures to be performed with unencoded, unregistered, minimally calibrated robots while removing the constraint of placing the needle tip on a mechanically enforced Remote Center of Motion (RCM).
  
  
  METHODS
  The algorithm requires only online tracking of the surgical tool and a five-degree-of-freedom (5-DOF) robot comprising three prismatic DOF and two rotational DOF. An incremental adaptive motion control cycle guides the needle to the insertion point and also orients it to align with the target-entry-point line. The robot executes RCM motion without having a physically constrained fulcrum point.
  
  
  RESULTS
  The proof-of-concept prototype system achieved 0.78 mm translation accuracy and 1.4 degrees rotational accuracy (this is within the tracker accuracy) within 17 iterative steps (0.5-1 s).
  
  
  CONCLUSIONS
  This research enables robotic assistant systems for image-guided percutaneous procedures to be prototyped/constructed more quickly and less expensively than has been previously possible. Since the clinical utility of such systems is clear and has been demonstrated in the literature, our work may help promote widespread clinical adoption of this technology by lowering system cost and complexity.
authors.affiliation: Engineering Research Center for Computer Integrated Surgical Systems and Technology, Jones Hopkins University, Baltimore, Maryland 21218, USA. eboctor@ieee.org
authors.forename: Emad M
authors.initials: EM
authors.lastname: Boctor
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Webster
authors.forename: Herve
authors.initials: H
authors.lastname: Mathieu
authors.forename: Allison M
authors.initials: AM
authors.lastname: Okamura
authors.forename: Gabor
authors.initials: G
authors.lastname: Fichtinger
mesh_terms: D000465:Algorithms; D004867:Equipment Design; D021621:Imaging, Three-Dimensional; D009339:Needles; D012371:Robotics; D025321:Surgery, Computer-Assisted / Q000295:instrumentation