Three-dimensional geometric modeling of the cochlea

Three-dimensional geometric modeling of the human cochlea not only provides a basis for preoperative planning and postoperative evaluation of cochlear implantation, but also facilitates medical education acid training. In this paper, the three-dimensional geometric modeling method of the cochlea has been developed. The central path of the cochlea is extracted fi om a spiral CT image volume by segmenting the cochlea and tracking through the cochlear canal. The central path is modeled by a helico-spiral. The first component in the helico-spiral model represents the projected central path onto a plane perpendicular to the modiolar axis, while the second component depicts the longitudinal stretching of the central path. A nonlinear least square minimization based algorithm is devised for the identification of intrinsic and extrinsic parameters of the helico-spiral representation of the cochlea. Numerical phantoms with added different noise levels up to standard deviation of 2 mm are synthesized according to the average parameters of the human cochlea to evaluate the accuracy. In real human cochlear studies, our model fits into the modiolar axis and the central path very well, allowing the calculation of length, height and angular positions needed for frequency mapping of multi-channel cochlear implant electrodes.