title: Accuracy of measurements on digital videostroboscopic images of the vocal folds.
abstract: OBJECTIVE
  The reliability of objective measurements on digital laryngeal images was investigated.
  
  
  METHODS
  The magnitude of the error of measurement of surface areas by visually tracing the outline was determined for three different areas: the area of the lesion and, during vibration, the glottal area on maximal opening of the vocal folds and the glottal area on maximal closing of the vocal folds.
  
  
  RESULTS
  The errors in these areas were 10% to 30%. The results suggest that the error is mainly due to the uncertainty of the real outline of areas with a vague boundary. Correction for differences in magnification between two images (posttherapy and pretherapy) is of importance in about 25% to 65% of cases, depending on the area measured.
  
  
  CONCLUSIONS
  Only when the magnification ratio is small (less than about +/- 10% from 1.0) may a correction not be necessary.
authors.affiliation: Institute of Phoniatrics, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Renée
authors.initials: R
authors.lastname: Speyer
authors.forename: George H
authors.initials: GH
authors.lastname: Wieneke
authors.forename: Willem
authors.initials: W
authors.lastname: Kersing
authors.forename: Philippe H
authors.initials: PH
authors.lastname: Dejonckere
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted; D007828:Laryngoscopy; D015588:Observer Variation; D010699:Phonation; D015203:Reproducibility of Results; D014741:Video Recording; D014827:Vocal Cords / Q000473:pathology* / Q000503:physiopathology; D014832:Voice Disorders / Q000503:physiopathology / Q000628:therapy