Real-Time Intracochlear Distance Sensing and Navigation Using a Dual Fiber Optical Coherence Tomography System

HYPOTHESIS: A dual fiber-based optical coherence tomography (OCT) system can be used for real-time intracochlear navigation and distance computation in the human cochlea. BACKGROUND: OCT is a contrast- and radiation-free modality that provides real-time 2- and 3-dimensional imaging of tissue microanatomy at higher resolutions than those of conventional MRI or CT. Because the fundamental working principle of OCT is to measure the time delay of backscattered near-infrared light using low-coherence interferometry, OCT functions as an intrinsic light-based distance sensor. METHODS: A single- and dual-fiber attached to a custom-built 1310 nm swept-source (SS) OCT system was validated in cochlear phantoms and tested in a human cadaveric cochlea to compute the distance of the fibers from the lateral and medial walls. Curvature and distance of the fibers to the lateral and medial walls of the scala tympani were obtained during insertion and pull-back of the fibers as accessed through a round window approach. RESULTS: Our fiber-based SS-OCT system can detect a maximum distance of 7.10 mm with an axial resolution of 10 µm at an acquisition speed of 8 µs. Using space-division multiplexing (SDM) for our dual fiber, we were able to simultaneously obtain distance measurements from 2 spatially separated locations without the need for mechanical rotation. Furthermore, our custom user interface provided an immediate 3-color-coded warning system, which facilitated real-time microadjustments of fiber trajectory to avoid intracochlear trauma. CONCLUSION: A dual fiber-based SDM-OCT system can be used to provide real-time spatial navigation and distance calculation to the cochlear walls.