Study On The Detection Of Spinal Cord Tension By Laser-Generated Surface Acoustic Wave

Currently,tethered cord syndrome(TCS)has been one of the most common diseases of the spinal cord.Patients with TCS are usually treated by cutting off the weight and bond at the bottom of the spinal cord to relieve the overstretch state.Up to now,doctors always rely on the clinical experience to judge the amount should be cut to make the spinal cord return to normal tension,which is not supported by any reliable basis.As a medical and engineer cross-project,this article focused on the quantitative information about the surface tension of the spinal cord,which will help doctors perform more accurate surgeries to avoid injury to the patient and reduce the risk of secondary surgery.After fully analyzing the background and purpose of the project,we presented a new non-destructive testing system based on the laser-generated surface acoustic wave(SAW).When the laser irradiates on the surface of spinal cord,it will generate the SAW,which contains the information of elastic parameters and geometrical characteristic of the spinal cord.And then,spinal cord surface tension can be measured by analyzing the propagation characteristics of SAW.The main content of this paper is as follows:1.The viscoelastic model of spinal cord was established by analyzing its structure and physical characteristics.After explored a variety of stress detection programs,we chose the laser-generated SAW technology to design the system.Then we introduced the excitation principle and propagation theory of SAW in detail.2.The finite element analysis was carried out by COMSOL.A simulation model of pulsed laser induced SAW was established.After that,the attenuation characteristics of SAW on the surface of the spinal cord was studied.According to the acoustic elasticity theory,with related analysis principles,the relationship between the propagation time difference of SAW signal and tensile stress was established,and the curve fitting was carried out,which realized the quantitative detection.The influencing factors of SAW signal are simulated and analyzed,which provided theoretical guidance for the experiment and mutual verification with the experimental results.3.The SAW detection system based on PVDF piezoelectric film was designed and built.The experiments were carried out on porcine spinal cord samples.The attenuation characteristics of SAW on the surface of the spinal cord was analyzed through collected SAW signals.The SAW signals under different stretch state were collected at detection points,and then the relationship between the propagation time difference of SAW and tensile stress was established,which was compared with the simulation results to prove the feasibility of the system.Through multiple data collection in the same conditions,the system repeatability and the stability of the initial state were verified.The result showed that it was feasible and effective to detect spinal cord tension by laser-generated SAW technology.The relationship between SAW signal and the surface tension of spinal cord was established.Finally,we achieved quantitative detection of spinal cord tension,which will contribute to the accurate diagnosis and treatment of TCS.