KEYWORDS: Cochlea, Electrodes, Digital signal processing, Calibration, Surgery, Spatial resolution, Signal processing, Navigation systems, Frequency response, Reflectometry
Cochlear implantation surgery is the only available treatment to restore hearing for individuals afflicted with severe to profound sensorineural hearing impairment. This procedure involves the precise insertion of a cochlear electrode array (EA), within constrained anatomical spaces with bending radii as minimal as 2 mm. During the insertion of EAs, surgeons primarily face two challenges: the potential for cochlear damage and the ideal positioning of the EA within the cochlear pathway. Although the use of EAs fitted with fiber Bragg grating sensors has shown successful real-time force monitoring, its effectiveness for precise placement is hindered by its low spatial resolution, making accurate EA positioning acquisition difficult. This study investigates the use of an optical frequency domain reflectometry (OFDR) sensing system, which has a spatial resolution of 0.65 mm to aid in the precise positioning of EAs during insertion. We demonstrate that by using OFDR sensing technology, a bare single-mode silica optical fiber with cladding and coating diameters of 50 μm and 105 μm, respectively, could be used to pinpoint the exact location of an EA. The frequency shift response along the fiber length correlates with the bending radius of the CI model, underscoring the potential of OFDR sensing technology to assist in EA positioning during cochlear implantation surgery.
We report an orientation-sensitive omnidirectional vibration sensor based on fiber Bragg gratings (FBGs) inscribed in a seven-core optical fiber. By monitoring the central wavelength shifts of three FBGs in the central core and two outer cores, orientation information in 0-180° range as well as the acceleration value are obtained. The performance of the vibration sensor is characterized at different frequencies, orientations and accelerations. Comparison results for orientation discrimination using different groups of outer cores are investigated to enhance the reliability of the vibration sensor. The experimental results demonstrate an accuracy as high as 0.01° for orientation discrimination. The compact size and simple structure make the vibration sensor potentially superior in industrial applications where precise monitoring of the orientation is a necessity.
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