Automatic determination of optimal surgical drilling trajectories for cochlear implant surgery

Abstract

Cochlear implantation is a surgical procedure in which an electrode array is permanently implanted in the cochlea to stimulate the auditory nerve and allow deaf people to hear. Traditional techniques require wide excavation of the temporal bone to ensure that the surgeon does not damage sensitive structures. Recently, a new minimally invasive approach was proposed in which a single hole is drilled on a straight trajectory from skull surface to the cochlea and allows the trajectory to be chosen pre-operatively in a CT. A major challenge with this approach is to determine, in the CT, a safe and effective drilling trajectory, i.e., a trajectory that with high probability avoids vital structures and effectively reaches the cochlea. These features lie within a few millimeters, the drill is one millimeter in diameter, and drill positioning errors are approximately a half a millimeter root-mean square. Thus, trajectory selection is both difficult and critical to the success of the surgery. In this thesis, a method is presented for finding optimal drilling trajectories with an approach designed to maximize safety under conditions of drill positioning error. Results are compared with trajectories chosen manually by an experienced surgeon. In tests on thirteen cases, the technique is shown to find approximately twice as many acceptable trajectories as those found manually.