Pressure in the Cochlea during Infrared Irradiation

Nan Xia, Xiaodong Tan, Yingyue Xu, Wensheng Hou, Teresa Mao, Claus Peter Richter*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Objective: The purpose of the study is to demonstrate laser-evoked pressure waves in small confined volumes such as the cochlea. Methods: Custom-fabricated pressure probes were used to determine the pressure in front of the optical fiber in a small dish and patch pipettes to measure temperature changes. Pressure probes were inserted into scala tympani (ST) or vestibuli during laser stimulation. With a sensitive microphone the pressure was measured in the outer ear canal. Results: Heating was spatially confined. The heat relaxation time was 35 ms. During laser stimulation in the cochlea at 17 μJ/pulse, the pressure in the outer ear canal (EC) was 43.5 dB (re 20 μPa). The corresponding intracochlear pressure was calculated to be about 78.5 dB (re 20 μPa) using the middle ear reverse transfer function of -35 dB. At 164 μJ/pulse, the pressure in the EC was on average 63 dB (re 20 μPa) and the intracochlear pressure was estimated to be 98 dB (re 20 μPa), which is similar to the value obtained with the pressure probe, 100 dB (re 20 μPa). Side-emitting optical fibers were used to steer the beam path. The pressure values were independent of the orientation of the beam path. Evoked compound action potentials of the auditory nerve were maximum when spiral ganglion neurons were in the beam path. Conclusion: Pressure waves are generated during infrared laser stimulation. The intracochlear pressure was independent from the orientation of the beam path. Significance: Neural responses required the spiral ganglion neurons to be directly irradiated.

Original languageEnglish (US)
Pages (from-to)1575-1584
Number of pages10
JournalIEEE Transactions on Biomedical Engineering
Volume65
Issue number7
DOIs
StatePublished - Jul 2018

Keywords

  • Auditory system
  • cochlea
  • infrared radiation
  • optical radiation effects
  • photoacoustic effect

ASJC Scopus subject areas

  • Biomedical Engineering

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