title: Phasegram Analysis of Vocal Fold Vibration Documented With Laryngeal High-speed Video Endoscopy.
abstract: BACKGROUND
  In a recent publication, the phasegram, a bifurcation diagram over time, has been introduced as an intuitive visualization tool for assessing the vibratory states of oscillating systems. Here, this nonlinear dynamics approach is augmented with quantitative analysis parameters, and it is applied to clinical laryngeal high-speed video (HSV) endoscopic recordings of healthy and pathological phonations.
  
  
  METHODS
  HSV data from a total of 73 females diagnosed as healthy (n = 42), or with functional dysphonia (n = 15) or with unilateral vocal fold paralysis (n = 16), were quantitatively analyzed. Glottal area waveforms (GAW) and left and right hemi-GAWs (hGAW) were extracted from the HSV recordings. Based on Poincaré sections through phase space-embedded signals, two novel quantitative parameters were computed: the phasegram entropy (PE) and the phasegram complexity estimate (PCE), inspired by signal entropy and correlation dimension computation, respectively.
  
  
  RESULTS
  Both PE and PCE assumed higher average values (suggesting more irregular vibrations) for the pathological as compared with the healthy participants, thus significantly discriminating healthy group from the paralysis group (P = 0.02 for both PE and PCE). Comparisons of individual PE or PCE data for the left and the right hGAW within each subject resulted in asymmetry measures for the regularity of vocal fold vibration. The PCE-based asymmetry measure revealed significant differences between the healthy group and the paralysis group (P = 0.03).
  
  
  CONCLUSIONS
  Quantitative phasegram analysis of GAW and hGAW data is a promising tool for the automated processing of HSV data in research and in clinical practice.
authors.affiliation: Voice Research Laboratory, Department of Biophysics, Faculty of Science, Palacký University Olomouc, Tr. 17. listopadu 12, 771 46 Olomouc, Czech Republic. Electronic address: herbst@ccrma.stanford.edu.
authors.forename: Christian T
authors.initials: CT
authors.lastname: Herbst
authors.affiliation: Institute of Imaging & Computer Vision, RWTH Aachen University, Kopernikusstr. 16, 52074 Aachen, Germany.
authors.forename: Jakob
authors.initials: J
authors.lastname: Unger
authors.affiliation: Institute for Theoretical Biology, Humboldt University Berlin, Invalidenstraße 43, 10115 Berlin, Germany.
authors.forename: Hanspeter
authors.initials: H
authors.lastname: Herzel
authors.affiliation: Voice Research Laboratory, Department of Biophysics, Faculty of Science, Palacký University Olomouc, Tr. 17. listopadu 12, 771 46 Olomouc, Czech Republic.
authors.forename: Jan G
authors.initials: JG
authors.lastname: Švec
authors.affiliation: Department of Computer Science, University of Applied Sciences, Schneidershof, 54293 Trier, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Lohscheller
mesh_terms: D000328:Adult; D000368:Aged; D001331:Automation; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D055154:Dysphonia / Q000175:diagnosis* / Q000503:physiopathology; D019277:Entropy; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007828:Laryngoscopy / Q000379:methods*; D008875:Middle Aged; D017711:Nonlinear Dynamics; D010507:Periodicity; D010699:Phonation; D011237:Predictive Value of Tests; D013997:Time Factors; D014732:Vibration; D014741:Video Recording / Q000379:methods*; D014826:Vocal Cord Paralysis / Q000175:diagnosis* / Q000503:physiopathology; D014827:Vocal Cords / Q000503:physiopathology*; D014833:Voice Quality
keywords: glottal area waveform; high-speed video endoscopy; nonlinear analysis; periodicity; phasegram