Digital X-ray stereophotogrammetry for cochlear implantation

Multielectrode, intracochlear implant systems are effective treatment for p rofound sensorineural hearing loss. In some cases, these systems do not per form well, which may be partially due to variations in implant location wit hin the cochlea, Determination of each electrode's position in a patient's inner ear provides an in vivo basis for both the cochlear modeling of elect rical fields and the future design of electrode arrays that deliver electri cal stimulation to surviving auditory neurons, and may improve speech proce ssor programming for better speech recognition. We developed an X-ray stere ophotogrammetric approach to localize implanted electrodes in three dimensi ons. Stereophotogrammetry of implanted electrodes is formulated in weak per spective geometry, with knowledge of a three-dimensional (3-D) reference st ructure and electrode positions in each of two digital stereo-images. The l ocalization error is theoretically, numerically, and experimentally quantif ied. Both numerical and experimental results demonstrate the feasibility of the technique.