title: Ray-casting based evaluation framework for haptic force feedback during percutaneous transhepatic catheter drainage punctures.
abstract: OBJECTIVE
  Development of new needle insertion force feedback algorithms requires comparison with a gold standard method. A new evaluation framework was formulated and tested on needle punctures for percutaneous transhepatic catheter drainage (PTCD).
  
  
  METHODS
  Needle insertion is an established procedure for minimally invasive interventions in the liver. Up-to-date, needle insertions are precisely planned using 2D axial CT slices from 3D data sets. To provide a 3D virtual reality and haptic training and planning environment, the full segmentation of patient data is often a mandatory step. To lessen the time required for manual segmentation, we propose direct haptic volume-rendering based on CT gray values and partially segmented patient data. The core contribution is a new force output evaluation method driven by a ray-casting technique that defines paths from the skin to target structures, i.e., the right hepatic duct near the juncture with the common hepatic duct. A ray-casting method computes insertion trajectories from the skin to the duct considering no-go structures and plausibility criteria. A rating system scores each trajectory. Finally, the best insertion trajectories are selected that reach the target. Along the selected paths, force output comparison between a reference system and the new haptic force output algorithm is carried out, quantified and visualized.
  
  
  RESULTS
  The evaluation framework is presented along with an exemplary study of the liver using the atlas data set from a reference patient. In a comparison of our reference method to a newer algorithm, force outputs are found to be similar in 99% of the paths.
  
  
  CONCLUSIONS
  The proposed evaluation framework allows reliable detection of problematic PTCD trajectories and provides valuable hints to improve force feedback algorithm development.
authors.affiliation: Institute of Medical Informatics, University of Lübeck, Lübeck, Germany, mastmeyer@imi.uni-luebeck.de.
authors.forename: Andre
authors.initials: A
authors.lastname: Mastmeyer
authors.forename: Tobias
authors.initials: T
authors.lastname: Hecht
authors.forename: Dirk
authors.initials: D
authors.lastname: Fortmeier
authors.forename: Heinz
authors.initials: H
authors.lastname: Handels
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004322:Drainage / Q000379:methods*; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging* / Q000601:surgery; D011677:Punctures; D011860:Radiography, Abdominal; D014057:Tomography, X-Ray Computed / Q000379:methods*