OFDR-based navigation system for minimally invasive cochlear implantation

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.