Design And Research Of Ultrasonic Transducer Used For Nerve Conduction Block

BackgroundTraditional ultrasonic physiotherapy equipment mainly uses low ultrasonic thermal effects and mechanical effects to "heat" or massage mechanical tissues to relieve pain,relieve fatigue,and promote blood circulation,without taking into account excitement in the nerves.The conduction process of the fiber,and also does not combine the permeability of potassium and sodium ion channels with ultrasonic physiotherapy.This study focuses on the physical modeling and analysis of nerve conduction block and its mechanism based on the conduction process of excitement on nerve fibers.In ultrasonic physiotherapy based on nerve conduction block,a multi-focus sound field distribution in a dot arrangement is required.In the practical application of ultrasound,the technologies for realizing the multi-focus sound field with point distribution are phased array transducer and acoustic lens transducer.Ultrasonic phased array transducers have high costs and complicated manufacturing processes.A large number of array elements are required to focus the transducer at a sufficient depth to achieve a good focusing effect.The main advantage of the ultrasonic lens compared to the phased array is that it is easy to construct and cheap,and it is more suitable for the domestic scene mode of ultrasonic physiotherapy.Therefore,the piezoelectric ceramic combined acoustic lens can be used to obtain the bifocal sound field distribution,and then use the two The interference between the two focal points creates side lobes to achieve a multi-focus sound field arranged in a dot pattern.ObjectiveBased on the analysis of the conduction of excitement on nerve fibers,it is believed that when ultrasound stimulation is performed on neurons,a bifocal sound field distribution is required.Therefore,this study proposes and basically implements two focal plane bifocal transducer designs and one acoustic axis transducer design,in order to expect the bifocal transducer to provide a theoretical reference when the ultrasound physiotherapy acts on nerve stimulation.Methods1.Through the discussion of the conduction process of excitement on nerve fibers and the mechanism of nerve block,the theoretical relationship between action potential and potassium and sodium ion channel inactivation was found,and then the corresponding physical model was established and the method needed to improve nerve block was analyzed.Finally,find out the specific means of implementation of the method.2.Based on the principle of multi-focus sound field with point distribution,a planar piezoelectric ceramic combined concave acoustic lens transducer is proposed.The design idea is mainly to divide the concave acoustic lens into two spherical surfaces and place one of the spherical surfaces along the longitudinal axis.The axis moves horizontally upwards to reach the design goal of the focal plane dual-focus transducer,and the side lobe is generated through the interference between the two focal points to achieve a multi-focus sound field with a dot arrangement.The theoretical sound field calculation of this transducer was carried out using the calculation idea of Rayleigh integral,the sound field distribution was simulated by matlab,and the suitable parameters of the sound field distribution were selected for mechanical processing,and finally carried out Hydrophone sound field detection and result analysis.3.The design concept of the second concave spherical shell self-focusing combined cone acoustic lens comes from interference theory.Ultrasound will focus on a point after passing through the concave spherical shell piezoelectric ceramic sheet,after passing through the cone lens,after refraction,it will be divided into two Wavefronts are coherent sound sources.According to the theory of interference,the sound wave surfaces of two coherent sound sources produced by a point sound source after passing through a conical lens will be superimposed on the focusing area,and interference will form a point-like multi-focus sound field distribution.After that,the sound field simulation and calculation were carried out,the appropriate transducer parameters were selected for mechanical processing,and finally the hydrophone detection and result discussion and analysis were carried out.4.In the actual propagation of ultrasound,when the ultrasound passes through different media,due to the difference in acoustic impedance,the ultrasound will reflect and transmit at the interface between the two media.Based on this feature,the output interface of the acoustic lens should not simply be regarded as a pure lens model with only transmission but no reflection.The transmission process of the analog light wave in the resonant cavity can be regarded as an acoustic resonant cavity model that transmits and reflects multiple times in the acoustic field,and realizes a multi-focus sound field with dots arranged on the acoustic axis.Theoretically,the distance distribution of the focal point on the acoustic axis is calculated according to the transmission matrix,the appropriate transducer parameters are selected for mechanical processing,and finally the hydrophone detection and results are discussed and analyzed.Results1.Compared with acoustic,magnetic,and light neuron stimulation methods,ultrasound stimulation is favored by researchers for its non-invasive,high stimulation depth and high spatial resolution.In time,the inversion time of potassium and sodium ion channels is about milliseconds.Ultrasound can generate ultrasound pulses corresponding to milliseconds,which helps to activate the state of nerve conduction block.In space,the multi-focal focus area of the spot arrangement generated by the ultrasonic transducer can cause the relative displacement of the neuron fiber compared with the non-focus area,and the multi-focus sound field of the spot arrangement can be larger The nerve excitement area and faster nerve conduction speed help to activate the state of nerve conduction block in ultrasound physiotherapy.Therefore,when stimulating nerve fibers,multi-focus focused ultrasound stimulation with dot arrangement is what we need.2.The integral expression of the sound field of the bifocal acoustic lens transducer calculated by Rayleigh integration is input into the matlab simulation software for multiple simulation results comparison,and one of the best set of parameters of the dual lens transducer is selected,of which the great circle The diameter is 95 mm,the diameter of the small circle is 76 mm,the radius of curvature is 55 mm,and the distance between the two focal points is 4mm.The simulation results can see obvious double peaks,and the shape of the acoustic focal area is better,and the focusing effect is better.After the mechanical processing,the piezoelectric ceramic hydrophone is detected.Although the second focus peak of the bifocal transducer is low,the design of the focal plane bifocal transducer is basically realized,and it can be passed between the focal points.Interference forms side lobes to achieve a point-like multifocal sound field distribution.3.The sound field calculation method of the concave spherical shell self-focusing combined cone acoustic lens focal plane transducer still adopts the Rayleigh integral expression,substitutes different coordinate systems and compares the simulation results for many times,and the selected transducer parameter distribution is caliber It is 58 mm,the inner diameter of the spherical shell is 34 mm,the outer diameter is 36 mm,and the distance from the transducer to the lens plane is 8mm.The simulation results can see obvious double peaks,and the shape of the acoustic focal area is better,and the focusing effect is better.After mechanical processing,the sound field distribution of the piezoelectric ceramic hydrophone is good,and the design of the focal plane bifocal transducer is realized,and the side lobe can be formed through the interference between the focal points to achieve a point-like multi-focus sound field distribution.4.The calculation method of the acoustic field of the concave spherical shell self-focusing plano-convex acoustic lens transducer combines the optical transmission matrix and the Rayleigh integral expression.Through the analysis of the transmission matrix,the theoretical calculation will occur at 120 mm and 68 mm from the transducer output surface The two focal points on the acoustic axis,after measuring the hydrophone,found that the sound field distribution is ideal.Basically,the design of the acoustic axis dual-focus transducer is basically realized,and the side lobes can be formed through the interference between the focal points to reach the point shape multi-focus sound field distribution.ConclusionSuccessfully designed and fabricated three kinds of spot-shaped multi-focus sound field focused ultrasonic transducer designs,which are flat piezoelectric ceramic combined concave acoustic lens transducer,concave spherical shell self-focusing combined cone acoustic lens transducer and The concave spherical shell self-focusing combined plano-convex acoustic lens transducer has a sound field distribution that is in good agreement with the theory.It is expected to provide a theoretical reference when ultrasonic physiotherapy acts on nerve conduction disorders.