Establishment And Application Of A Numerical Model Of Inner Ear Structure In Guinea Pigs

Objective:Establishing three dimensional numerical model of bony labyrinth and membranous labyrinth structure in normal guinea pigs,accurately and intuitively show anatomical structure and the spatial location relationship of the labyrinth system.The morphology of the membranous labyrinth was measured in detail.The change of intensity of pressure in the inner ear,the flow velocity of inner lymph flow and the relationship between pressure inlet and outlet pressure and time were analyzed by numerical simulation.The research platform of biomechanical numerical model of inner ear system was established.By simulating the enlarged vestibular aqueduct structure,a numerical model of labyrinth in the inner ear of guinea pigs with large vestibular aqueduct was established.The corresponding calculated values of normal guinea pigs and enlarged vestibular aqueduct were compared and analyzed.And the physiological functions of vestibular aqueduct and the effect of enlarged structure of vestibular aqueduct on inner ear were simulated by digital simulation.The deafness mechanism of large vestibular aqueduct syndrome was further analyzed from the perspective of biomechanics.Methods:Guinea pigs with normal hearing were divided into matched group and experimental group for animal experiments.Matched group:?One live guinea pig was anesthetized by intraperitoneal injection of 4%chloral hydrate.No contrast agent was used.?One Rat head model:guinea pig's neck was quickly broken after anesthesia with 4%chloral hydrate.At normal room temperature,fresh rat heads were taken.Under the microscope and through the external auditory canal to destroy the oval window membrane in the middle ear of those rat heads.The middle ear tympanum were sealed with plaster.Then those rat heads were soaked in formalin solution for 24 hours.Experimental group:Four rat head model:four guinea pigs were labeled and named as 1?4.At the same room temperature,the mouse heads were placed in a mixture of formalin and iodine volts alcohol(the concentration ratio of the two was 1:1)to soak after the neck was broken and the oval window membrane was destroyed in the same process.The soaking time of no.1?4 specimens was 4,7,12 and 18 hours,respectively.Micro-CT scanning was performed in the experimental group and the control group,and imaging data in DICOM format were imported into Mimics20.0 for 3d modeling.After surface optimization,surface slice construction,gridding construction and surface fitting operation,the 3D model of normal guinea pig's bony labyrinth and membranous labyrinth system was obtained.The morphological measurement of the generated model was carried out with the measuring tool.Then the 3D model was imported into ANSYS18.0 for the numerical simulation of intensity of pressure in the inner ear of normal guinea pigs under external stimulation,the change of inner lymphatic flow velocity,and the pressure-time relationship at the pressure inlet and outlet.The diameter of the vestibular aqueduct in the thickened model was used to establish a numerical model of expanding vestibular aqueduct in the inner ear of guinea pigs,and the corresponding mechanical effects were calculated and analyzed by the same method.Finally,the simulation results of normal and enlarged vestibular aqueduct in guinea pigs were compared and analyzed.Results:(1)Morphological observation and measurement of the normal labyrinth system in guinea pigs:the cochlea tube is 3.75 weeks.The physical morphology measurements of the three membranous semicircular canals are shown in the table below,with an accuracy of 0.001.other data:The length of the total membrane foot was about 1.164mm,and the height,bottom-circumference diameter,surface area and volume of the cochlea were about 3.795mm.1.222mm.28.725mm2 and 3.986mm3.The vertical diameter of the elliptical sac was about 2.670mm,the transverse diameter was about 0.586mm.The vertical diameter of the utriculus was about 0.868mm.and the transverse diameter was about 0.785mm.The total volume of the semicircular canal and vestibular apparatus was about 3.175mm3.(2)When the inner ear structure is normal,1OOPa of pressure is given at the entrance of the endolymphatic sac.As the inner lymphatic fluid flows from the endolymphatic sac to the inner ear,the pressure gradually decreases and the flow rate gradually slows down.The pressure dropped to OPa,and the internal lymph flow rate dropped to Om/s in vestibule.(3)When the inner ear structure is normal,with the change of load time,the external force is approximately sinusoidal related to the pressure at the round window membrane,and finally tends to the equilibrium state.That is to say,the deformation amplitude of the round window membrane does not increase infinitely with the extension of load time,but tends to be stable.(4)When vestibular aqueduct expands,give endolymphatic sac entrance 100Pa pressure,as the inner lymphatic fluid flows from the endolymphatic sac to the inner ear,the pressure gradually decreases and the flow rate gradually slows down.The pressure range of vestibule,cochlea and part of semicircular canal was 1.000e?3.OOOePa,and the flow rate of internal lymph was 0?4.718e-4m/s.Conclusion:(1)By measuring the shape of the three-dimensional reconstruction model of the labyrinth of the inner ear of guinea pigs,detailed physical data of the labyrinth structure were obtained,which provided corresponding reference data for the quantitative analysis of the structure and function of the inner ear system.(2)A three-dimensional reconstruction numerical model of the bony labyrinth and the membranous labyrinth in guinea pigs was established to explore the pathogenesis of inner ear diseases such as large vestibular aqueduct syndrome and meniere's disease from the perspective of biomechanics.(3)Through numerical simulation analysis,it can be concluded that the normal vestibular aqueduct has the function of buffering pressure and limiting the flow rate of lymphatic fluid,and plays an important role in protecting the inner ear.The function of enlarged vestibular aqueduct to buffer pressure and limit the flow rate of lymphatic fluid is obviously weakened,and the inner ear is easily damaged when stimulated by external forces.The data of deafness mechanism of large vestibular aqueduct were obtained from the view of biomechanics.