Shear Wave Elastography For Measuring Muscle Stress Based On FEM

The problem of force distribution in muscles is a research hotspot.The existing detection methods,such as direct detection and detection of myoelectric signals,are faced with the predicaments of biological rejection and limited application scope.According to the research,the shear modulus changes during the process of muscle force,so the force of muscle can be studied by measuring the shear wave velocity.As a promising non-invasive imaging diagnosis and treatment method,shear wave elastography has recently been introduced into the research of muscle force problems.However,the existing studies of shear wave elastography for muscle stress mainly focus on experimental measurement and clinical testing of isolated muscles,and lack theoretical basis.Therefore,in this paper,the finite element method was adopted to esta'blish a hyperelastic finite element muscle model to study the variation of shear wave velocity under stress conditions and to explore the mathematical relationship between shear wave velocity and muscle force.It provides a theoretical basis for shear wave elastography to detect force distribution in muscles.In this paper,we first establish a hyperelastic finite element model based on the stress-strain curve measured from the fox extraocular muscles in vitro.According to the load value applied in the experiment,the initial stress is applied by the uniaxial stretching method,and then the point excitation method is used.A sinusoidal excitation is applied to simulate the shear wave elastography process and.calculate the shear wave velocity under stress.The simulation results show that as the load increases,the shear wave velocity increases linearly from 6.1m/s to 13.1m/s,and the relationship between force and shear wave velocity is proved theoretically.Secondly,through the test data of tendon materials,another hyperelastic model was established and the speed change under stress was calculated by repeating the simulation experiment.The simulation results of the tendon model show that with the increase of.the applied load,the shear wave velocity increases linearly from 14.2m/s to 27.89m/s,which again proves the relationship between force and shear wave velocity.Finally,the difference between the shear wave velocity calculated by the tendon simulation and the experimental measurement is analyzed,and the model is corrected.After the correction,the simulated shear wave velocity is basically consistent with the experimental data under the same stress.