title: Distances between facial landmarks can be measured accurately with a new digital 3-dimensional video system.
abstract: BACKGROUND
  The aim of this study was to investigate a new digital 3-dimensional infrared video system to determine its accuracy, precision, and validity in measuring facial distances.
  
  
  METHODS
  Bench experiments were performed by measuring the vertical and diagonal distances of chessboard squares of known length to determine the system's accuracy and precision. To test the system's validity, 16 healthy volunteers participated in this study. Vertical and horizontal distances of the face were measured electronically at rest, and on posed and aggressive smiles. All measurements were repeated after 8 weeks. Direct measurements of the intercanthal distance were obtained twice with calipers.
  
  
  RESULTS
  A minor systematic error was found in the bench experiments, with the highest absolute error of 0.227 +/- 0.39 mm. The analysis with this video system showed good reproducibility of all measured distances when the mean of 2 frames was used to compare distances. Digital measurements of the intercanthal distances showed high agreement with the clinically obtained values.
  
  
  CONCLUSIONS
  This digital video system can measure geometric distances in a 3-dimensional environment with high precision. Facial distances can be measured with good accuracy and precision, allowing applications in research and clinical practice.
authors.affiliation: Senior research assistant, Department of Gerodontology and Removable Prosthodontics, University of Geneva, Geneva, Switzerland. martin.schimmel@unige.ch
authors.forename: Martin
authors.initials: M
authors.lastname: Schimmel
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Christou
authors.forename: Odyssia
authors.initials: O
authors.lastname: Houstis
authors.forename: François R
authors.initials: FR
authors.lastname: Herrmann
authors.forename: Stavros
authors.initials: S
authors.lastname: Kiliaridis
authors.forename: Frauke
authors.initials: F
authors.lastname: Müller
mesh_terms: D000328:Adult; D019985:Benchmarking; D002508:Cephalometry / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D004431:Ear, External / Q000033:anatomy & histology; D004867:Equipment Design; D005123:Eye / Q000033:anatomy & histology; D005138:Eyebrows / Q000033:anatomy & histology; D005143:Eyelids / Q000033:anatomy & histology; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D007259:Infrared Rays; D008046:Lip / Q000033:anatomy & histology; D008297:Male; D009666:Nose / Q000033:anatomy & histology; D015203:Reproducibility of Results; D012904:Smiling; D014741:Video Recording / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D055815:Young Adult