Three-dimensional geometric modeling of the cochlea using helico-spiral approximation

In this paper, the three-dimensional geometry of the human cochlea is model ed by the helico-spiral seashell model. The 3-D helico-spiral model, the ge neralized representation of the Archimedian spiral model, provides a framew ork for measuring cochlear features based on consistent estimation of model parameters. Nonlinear least square minimization based algorithms are devel oped for the identification of rotation, center and intrinsic parameters of the helico-spiral representation. Two algorithms are designed for the rota tion axis aligned to the modiolar axis: one is more susceptible in the pres ence of noise, while the other allows applicability to two-dimensional data sets. The estimated center and intrinsic parameters allow the calculation of length, height and angular positions needed for frequency mapping of mul tichannel cochlear implant electrodes. Model performance is evaluated with numerically synthesized curves with different levels of added random noise, histologic data and real human cochlear spiral computed tomography data.