Clin Exp Otorhinolaryngol.  2016 Jun;9(2):98-103. 10.21053/ceo.2015.00542.

Methodology for Intraoperative Laser Doppler Vibrometry Measurements of Ossicular Chain Reconstruction

• SokoÅ‚owski J
• Lachowska
• Bartoszewicz R
• Niemczyk K

• KMID: 2165050
• DOI: http://doi.org/10.21053/ceo.2015.00542

Abstract

OBJECTIVES
Despite the increasing number of research concerning the applications of the Laser Doppler Vibrometry (LDV) in medicine, its usefulness is still under discussion. The aim of this study is to present a methodology developed in our Department for the LDV intraoperative assessment of ossicular chain reconstruction.
METHODS
Ten patients who underwent "second look" tympanoplasty were involved in the study. The measurements of the acoustic conductivity of the middle ear were performed using the LDV system. Tone bursts with carrier frequencies of 500, 1,000, 2,000, and 4,000 Hz set in motion the ossicular chain. The study was divided into four experiments that examined the intra- and interindividual reproducibility, the utility of the posterior tympanotomy, the impact of changes in the laser beam angle, and the influence of reflective tape presence on measurements.
RESULTS
There were no statistically significant differences between the two measurements performed in the same patient. However, interindividual differences were significant. In all cases, posterior tympanotomy proved to be useful for LDV measurements of the ossicular prosthesis vibrations. In most cases, changing the laser beam angle decreased signal amplitude about 1.5% (not significant change). The reflective tape was necessary to achieve adequate reflection of the laser beam.
CONCLUSION
LDV showed to be a valuable noncontact intraoperative tool for measurements of the middle ear conductive system mobility with a very good intraindividual repeatability. Neither a small change in the angle of the laser beam nor performing the measurements through posterior tympanotomy showed a significant influence on the results. Reflective tape was necessary to obtain good quality responses in LDV measurements.

Keyword

Otitis Media; Hearing Loss, Conductive; Ear, Middle; Ossicular Prosthesis; Tympanoplasty

MeSH Terms

Acoustics
Ear, Middle
Hearing Loss, Conductive
Humans
Ossicular Prosthesis
Otitis Media
Tympanoplasty
Vibration

Figure

• 

  Fig. 1. Refl ective foil attached to the “long columella” prosthesis just before Laser Doppler Vibrometry measurements started. View through the posterior tympanotomy. EChoG, electrocochleaogra-phy; this electrode was used in addition for acoustical hearing moni-toring during surgery (auditory evoked potentials measurements) that are not presented in this study.

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  Fig. 2. The average velocity measured for each carrier frequency in each case separately (n=10). The horizontal axis shows the patient number, and the vertical axis represents the averaged measured velocity.

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  Fig. 3. The intensity of the reflected beam (%) in regards to the surface of interest with the attached reflective tape. The highest reflectance was obtained from the ossicular prosthesis and the lowest from the round window.

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  Fig. 4. The percentage change of the reflected laser beam with regard to the 30° (blue color) and 10° (yellow color) change in the angle of the outgoing laser beam. As shown, the 10° angle change results in less change in reflected laser beam than 30°

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