High-frequency ultrasound Doppler velocimetry measurements of intra-cochlear structures in human temporal bones.

Abstract

Hearing loss is one of the most prevalent, chronic, and fast growing disorders, affecting approximately one-tenth of the population. Diagnostic imaging tools currently used in this field such as CT and MRI do not have sufficient spatial/temporal resolution to properly diagnose most of the underlying causes of hearing loss. In this work, we present the first high-resolution velocimetry measurements of intra-cochlear structures using high-frequency (40 MHz) pulsed-wave Doppler ultrasound. A 40-MHz single-element transducer based on PMN-PT single-crystal piezoelectric was fabricated in-house and mounted onto the tip of a needle. The transducer was a side-looking circular disk with a 1 mm outer diameter. A custom data acquisition system was developed in order to perform pulsed-wave Doppler and was synchronized with an acoustic stimulus. Velocimetry measurements were performed on the basilar membrane located inside the cochlea of fresh temporal bones by imaging across the round window membrane and stimulating the eardrum with pure-tone sounds. For the first time, the vibration of the basilar membrane was measured on a completely intact cochlea using ultrasound velocimetry. The middle ear resonance could be detected by measuring the frequency-dependent basilar membrane velocities between 100 and 2500 Hz. This resonance was verified using a laser vibrometer.