Biomedical subjects

Chenkai Dai

Publications and source records attributed to Chenkai Dai.

3 recordsLinked to original sources

PubMed2006

Viscoelastic properties of human tympanic membrane.

The tympanic membrane or eardrum of human ear transfers sound waves into mechanical vibration from the external ear canal into the middle ear and cochlea. Mechanical properties of the tympanic membrane (TM) play an important role in sound transmission through the ear. Although limited resources about linear elastic properties of the TM are available in literature, there is a lack of measurement or modeling of viscoelastic properties of the TM at low stress levels. In this study, the uniaxial tensile, stress relaxation, and failure tests were conducted on fresh human cadaver TM specimens to explore mechanical properties of the TM. The experimental results were analyzed using the hyperelastic Ogden model and digital image correlation method. The constitutive equation and non-linear elastic properties of the TM were presented by functions of the stress and strain at the stress range from 0 to 1 MPa. Viscoelastic properties of the TM were described by the stress relaxation function and hysteresis. The results show that the uniaxial tensile test with the aid of digital image correlation analysis is a reliable and useful approach for measuring mechanical properties of ear tissues. The data presented in this paper contribute to ear biomechanics in both experimental measurement and theoretical analysis of ear tissues.

Cadaver↗

PubMed2006

Laser interferometry measurements of middle ear fluid and pressure effects on sound transmission.

An otitis media with effusion model in human temporal bones with two laser vibrometers was created in this study. By measuring the displacement of the stapes from the medial side of the footplate, the transfer function of the middle ear, which is defined as the displacement transmission ratio (DTR) of the tympanic membrane to footplate, was derived under different middle ear pressure and fluid in the cavity with a correction factor for cochlear load. The results suggest that the DTR increases with increasing frequency up to 4k Hz when the middle ear pressure was changing from 0 to 20 or -20 cm H20 (e.g., +/-196 daPa) and fluid level was increasing from 0 to a full middle ear cavity. The positive and negative pressures show different effects on the DTR. The effect of fluid on DTR varies between three frequency ranges: f < 1k, between 1k and 4k, and f > 4k Hz. These findings show how the efficiency of the middle ear system for sound transmission changes during the presence of fluid in the cavity and variations of middle ear pressure.

Bone Conduction↗

PubMed2003

[Integrated methods for assessing auditory nerve-auditory pathway integrity].

OBJECTIVE: To evaluate the feasibility and value of integrated methods to assess auditory pathway integrity. METHOD: Twenty-four cases of bilateral profoundly-deafened individuals who were considered as the candidates of cochlear implantation were included in this study. Auditory pathway integrity from these candidates of cochlear implantation were assessed with the integrated methods established by our team, which consist of 5 categories including 1. audiological test; 2. radiological imaging study; 3. ear-canal electric audiometry; 4. response to sound in daily life; and 5. speech development. RESULT: Twenty-three candidates who meet the criteria of auditory nerve-auditory pathway integrity received cochlear implantation with improved hearing and speech development postoperatively. The remainder one of the 24 candidates was diagnosed as bilateral absence of auditory nerve. The fault of cochlear implantation was avoided. CONCLUSION: The integrated methods for assessing auditory pathway integrity is feasible and valuable. Auditory nerve-auditory pathway integrity should be considered and included as one of the most important criteria for cochlear implantation candidate.

Acoustic Stimulation↗