title: Accuracy and Reliability of the Kinect Version 2 for Clinical Measurement of Motor Function.
abstract: BACKGROUND
  The introduction of low cost optical 3D motion tracking sensors provides new options for effective quantification of motor dysfunction.
  
  
  OBJECTIVE
  The present study aimed to evaluate the Kinect V2 sensor against a gold standard motion capture system with respect to accuracy of tracked landmark movements and accuracy and repeatability of derived clinical parameters.
  
  
  METHODS
  Nineteen healthy subjects were concurrently recorded with a Kinect V2 sensor and an optical motion tracking system (Vicon). Six different movement tasks were recorded with 3D full-body kinematics from both systems. Tasks included walking in different conditions, balance and adaptive postural control. After temporal and spatial alignment, agreement of movements signals was described by Pearson's correlation coefficient and signal to noise ratios per dimension. From these movement signals, 45 clinical parameters were calculated, including ranges of motions, torso sway, movement velocities and cadence. Accuracy of parameters was described as absolute agreement, consistency agreement and limits of agreement. Intra-session reliability of 3 to 5 measurement repetitions was described as repeatability coefficient and standard error of measurement for each system.
  
  
  RESULTS
  Accuracy of Kinect V2 landmark movements was moderate to excellent and depended on movement dimension, landmark location and performed task. Signal to noise ratio provided information about Kinect V2 landmark stability and indicated larger noise behaviour in feet and ankles. Most of the derived clinical parameters showed good to excellent absolute agreement (30 parameters showed ICC(3,1) > 0.7) and consistency (38 parameters showed r > 0.7) between both systems.
  
  
  CONCLUSIONS
  Given that this system is low-cost, portable and does not require any sensors to be attached to the body, it could provide numerous advantages when compared to established marker- or wearable sensor based system. The Kinect V2 has the potential to be used as a reliable and valid clinical measurement tool.
authors.affiliation: Motognosis UG (haftungsbeschränkt), Berlin, Germany.
authors.forename: Karen
authors.identifier: http://orcid.org/0000-0002-3518-5274
authors.initials: K
authors.lastname: Otte
authors.affiliation: Motognosis UG (haftungsbeschränkt), Berlin, Germany.
authors.forename: Bastian
authors.initials: B
authors.lastname: Kayser
authors.affiliation: Motognosis UG (haftungsbeschränkt), Berlin, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Mansow-Model
authors.affiliation: Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany.
authors.forename: Julius
authors.initials: J
authors.lastname: Verrel
authors.affiliation: NeuroCure Clinical Research Center and Clinical and Experimental Multiple Sclerosis Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Experimental and Clinical Research Center, Max Delbrück Center for Molecular Medicine and Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Friedemann
authors.initials: F
authors.lastname: Paul
authors.affiliation: NeuroCure Clinical Research Center and Clinical and Experimental Multiple Sclerosis Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Experimental and Clinical Research Center, Max Delbrück Center for Molecular Medicine and Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Alexander U
authors.initials: AU
authors.lastname: Brandt
authors.affiliation: NeuroCure Clinical Research Center and Clinical and Experimental Multiple Sclerosis Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Schmitz-Hübsch
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D009038:Motion; D009043:Motor Activity; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D012984:Software