High-Frequency Ex vivo Ultrasound Imaging of the Auditory System

A 50 MHz array-based imaging system was used to obtain high-resolution images of the ear and auditory system. This previously described custom built imaging system (Brown et al., 2004, Brown et al., 2004, Brown and Gr, 2005) is capable of 50 μm axial resolution, and lateral resolution varying from 80 μm to 130 μm over a 5.12 mm scan depth. The imaging system is based on a 2 mm diameter, seven-element equal-area annular array, and a digital beamformer that uses high-speed field programmable gate arrays (FPGAs). The images produced by this system have shown far superior depth of field compared with commercially available single-element systems. Ex vivo, three-dimensional (3-D) images were obtained of human cadaveric tissues including the ossicles (stapes, incus, malleus) and the tympanic membrane. In addition, two-dimensional (2-D) images were obtained of an intact cochlea by imaging through the round window membrane. The basilar membrane inside the cochlea could clearly be visualized. These images demonstrate that high-frequency ultrasound imaging of the middle and inner ear can provide valuable diagnostic information using minimally invasive techniques that could potentially be implemented in vivo. (E-mail: J.Brown@dal.ca)