title: Endpoint Accuracy in Manual Control of a Steerable Needle.
abstract: OBJECTIVE
  To study the ability of a human operator to manually correct for errors in the needle insertion path without partial withdrawal of the needle by means of an active, tip-articulated steerable needle.
  
  
  METHODS
  The needle is composed of a 1.32-mm outer-diameter cannula, with a flexure joint near the tip, and a retractable stylet. The bending stiffness of the needle resembles that of a 20-gauge hypodermic needle. The needle functionality was evaluated in manual insertions by steering to predefined targets and a lateral displacement of 20 mm from the straight insertion line. Steering tasks were conducted in 5 directions and 2 tissue simulants under image guidance from a camera. The repeatability in instrument actuations was assessed during 100 mm deep automated insertions with a linear motor. In addition to tip position, tip angles were tracked during the insertions.
  
  
  RESULTS
  The targeting error (mean absolute error ± standard deviation) during manual steering to 5 different targets in stiff tissue was 0.5 mm ± 1.1. This variability in manual tip placement (1.1 mm) was less than the variability among automated insertions (1.4 mm) in the same tissue type. An increased tissue stiffness resulted in an increased lateral tip displacement. The tip angle was directly controlled by the user interface, and remained unaffected by the tissue stiffness.
  
  
  CONCLUSIONS
  This study demonstrates the ability to manually steer needles to predefined target locations under image guidance.
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology, Faculty of Mechanical, Maritime and Materials Engineering, Mekelweg 2, Delft 2628CD, The Netherlands. Electronic address: n.j.p.vandeberg@tudelft.nl.
authors.forename: Nick J
authors.initials: NJ
authors.lastname: van de Berg
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology, Faculty of Mechanical, Maritime and Materials Engineering, Mekelweg 2, Delft 2628CD, The Netherlands.
authors.forename: Jenny
authors.initials: J
authors.lastname: Dankelman
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology, Faculty of Mechanical, Maritime and Materials Engineering, Mekelweg 2, Delft 2628CD, The Netherlands.
authors.forename: John J
authors.initials: JJ
authors.lastname: van den Dobbelsteen
mesh_terms: D055011:Ablation Techniques / Q000295:instrumentation*; D001331:Automation; D001707:Biopsy, Needle / Q000295:instrumentation*; D055119:Elastic Modulus; D004867:Equipment Design; D005780:Gelatin / Q000737:chemistry; D006801:Humans; D008099:Liver / Q000601:surgery*; D009048:Motor Skills; D009339:Needles; D065287:Robotic Surgical Procedures / Q000295:instrumentation*; D013647:Task Performance and Analysis; D014741:Video Recording
chemical_list: D005780:Gelatin