| Bladder dysfunction caused by nerve injury is called neurogenic bladder in medicine.The current treatment and auxiliary urination measures include drug injection,operation,electrical stimulation,fistulization or urethral catheterization drainage,etc,but all of them are difficult to solve the neurogenic bladder problem effectively.Therefore,it is of practical significance to study the implantable auxiliary urination system.Based on the thermal effect of ultrasound and the theory of thermal power,a new method of using thermal power to assist dysfunction bladder urination was proposed in the early stage of our research group,and an implantable urination assist system driven by ultrasound vaporization steam was designed.In order to solve the problems of heat dissipation,saturated vapor pressure of working medium and biosafety of the driving capsule in this paper,the temperature rise characteristics of working medium were simulated,and the mathematical model of saturated steam pressure was established.The finite element model of biological tissue was established,and the biological safety of plane ultrasound and focused ultrasound was simulated respectively.The specific contents are as follows:1.The finite element simulation model of the driving capsule was established,the thermal interaction boundary conditions were set up,the distribution laws of the acoustic pressure field and the temperature field were simulated,and the accuracy of the simulation model was verified by the established simulation experiment platform.2.Based on the relationship between saturated vapor pressure and temperature,the mathematical model of driving pressure in prepressing period and micturition period was established.The mathematical model of urine flow was established by combining the theory of fluid mechanics and the characteristics of driving pressure,and the accuracy of the mathematical model was verified by the established simulation experiment platform.3.The finite element simulation model of abdominal biological tissue under the action of plane ultrasound was established,and the thermal interaction boundary condition was set up,and the distribution law of acoustic pressure field and temperature field of biological tissue under the action of different fat thickness and different sound intensity was simulated.4.The finite element simulation model of abdominal biological tissue under the action of concave spherical focused ultrasound and bowl shaped focused ultrasound was established,and the thermal interaction boundary condition was set up.The distribution rule of sound pressure field and temperature field of biological tissue under the influence of different fat thickness and different sound intensity was simulated and studied,and the effect of bowl shaped focused ultrasound and concave spherical focused ultrasound was compared and analyzed.The results show that: The simulation model and mathematical model are practical and effective.The working medium temperature and driving pressure can be increased by increasing sound intensity and ultrasonic radiation time.With the extension of radiation time,the growth rate of working medium temperature and driving pressure is slowing down gradually,and finally reaches the equilibrium state.On the premise of meeting the biological safety,the effects of various ultrasound on the urination assist system were compared,bowl focused ultrasound has the highest working efficiency,followed by concave spherical focused ultrasound,and plane ultrasound has the lowest.The results of this study can provide theoretical and technical guidance for animal and clinical trials of urinary assist system. |
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