Preoperative Evaluation Of Human Cochlear Geometry Based On Robotic Cochlear Implant

Robotic cochlear implant is an inevitable trend in the development of cochlear implants.However,due to individual differences in human cochlea,cochlear implant is highly susceptible to damage to the cochlea.Preoperative evaluation of cochlear geometry is an important basis for cochlear implants,which is of great significance for robotic cochlear implant.In this thesis,the preoperative evaluation of cochlear geometry was studied.A design method of scalable scala tympani model was proposed,and the implantation force detection experiment for perimodiolar electrode was carried out.The experimental results verified the necessity of preoperative evaluation of cochlear geometry and the superiority of robotic cochlear implant.Firstly,the human cochlear specimen was collected,and the Micro-CT images of the specimen were acquired by high-resolution CT scanning equipment.The Mimics platform was used to threshold segmentation of the images and separate the cochlear regions.The 3D model of human cochlea was reconstructed by 3D interpolation.Secondly,preoperative evaluation of cochlear geometry was performed.The cochlear model was re-segmented to obtain cross-section images of cochlear at four different angles.And an improved image processing method was designed to determine the center point of the cross-section of scala tympani.Combined with the specific geometric features of the cochlea,the central points were fitted by cubic B-spline interpolation to obtain the centerline of the scala tympani channel.Based on the centerline of the scala tympani channel,the geometric parameters of the cochlea were determined.The relationship between the cochlear duct length(CDL)and the geometric parameters of the cochlea was analyzed,and the formula for calculating the CDL value was determined.Furthermore,the geometry of the cochlea was analyzed in combination with the former research of the cochlear geometry.The applications of preoperative evaluation in the robotic cochlear implant system were concluded,and the initial implant path of the robot and the mathematical model of the scala tympani were obtained.Then,the design method of scalable scala tympani model was proposed.The mathematical model of the scala tympani was used as the central curve of scala tympani channel.Referring to the clinical anatomy data of the cochlea,the contour of the scala tympani cross-section was approximated as an ellipse.The profile was placed along the central curve,and the angle was adjusted to determine the position and orientation of the profile in three dimensions such that the central curve passes through its center.The virtual scala tympani model was generated in Solid Works,and the 2:1 fully transparent I-E scala tympani model and Cohen scala tympani model were fabricated by 3D printing to replace the specimen for experiment.Finally,the implant force measurement system for cochlear implant of perimodiolar electrode was established.The scala tympani model based on preoperative evaluation result was verified by experiment.The maximum robotic implant force of the I-E model was 0.0840 N,and the maximum robotic implant force of the Cohen model was 0.1335 N.The maximum manual implant force of the I-E model was 0.2379 N,and the maximum manual implant force of the Cohen model was 0.3034 N.The result showed that the robotic cochlear implant with I-E scala tympani model can obtain little implant force of perimodiolar electrode and reduce damage to the cochlea.