Research method of HIFU treatment sound field

At present, the methods for studying the sound field of HIFU piezo ceramic mainly include experimental measurement methods and numerical simulation methods.

The methods for measuring high-intensity ultrasonic sound fields are mainly hydrophones, ultrasonic radiation balances and fiber optic sensors.there are three methods.

(l) Hydrophone: It consists of a ring and a PVDF film that is internally tensioned, and its film thickness is 30~40 kn m, the metal film electrode is plated on the local area corresponding to both sides of the film, and the diameter at the center of the ring is less than in the region, polarization treatment is performed to obtain a piezoelectric effect. Because it has a small accepting transducer,There is no change in the original radiated sound field of HIFU piezoelectric transducer with arduino.

(2) Ultrasonic radiation balance: The sound intensity is obtained by measuring the radiation pressure of the ultrasonic wave, and the radiation sound pressure is that the sound beam produces a steady pressure on the obstacle in progress.

(3)Fiber optic sensor: by light source, transmission fiber, sensing element or modulation area, light detection.when temperature, pressure, acceleration, vibration, displacement has an effect on the optical path, the light wave will be characteristic parameters such as light intensity, wavelength, amplitude, etc. Resonance frequency of piezoelectric transducer change accordingly, and fiber optic sensors are based on these parameters.The relationship between external factors is used to detect the size of each corresponding physical quantity. It has anti-electromagnetic interference and is small size.High spatial resolution has the wide response bandwidth and extremely fast response speed.

Using numerical methods, it is possible to predict the actual focus area and its energy distribution in the human body.In recent years, the nonlinear simulation of HIFU piezoelectric ceramic element ultrasonic sound field has become a hot spot of many researchers. Many researchers have used these theories to study the simulation of acoustic nonlinear propagation. Zhang Dong of Boston University and Nanjing University respectively used the KzK equation and combined with the PelmeS heat conduction to excite the sine wave to perform the effects of ultrasonic linear and nonlinear characteristics on the sound field and temperature field. The sine wave excitation used in this method is different from the excitation waveform of the actual ultrasonic transducer. The focal field sound field formed by the sinusoidal excitation is different from the sound field formed by the ultrasonic transducer. Due to the large amount of simulation calculations and complex simulation methods of ESWL, the research results have not been applied to solve the problem of nonlinear ultrasonic wave propagation in the complex ESWL treatment. These methods are directly applied to simulate with different acoustic characteristics and irregularities. There is still a certain distance between the nonlinear propagation of sound waves in the soft tissue of the human body. Cleveland at Boston University in 2004 used FDTD simulation methods and ESWL treatment process under the assumption of two-dimensional plane and ultrasonic linear propagation.

The propagation characteristics of ultrasound Hifu piezoelectric ceramic transducer is in the middle kidney stones, but the algorithm is only used for the actual three-dimensional problem and a two-dimensional planar algorithm under the assumption that the nonlinear problem is linearized.The ultrasonic propagation equation of integral form is combined with genetic algorithm to simulate the sound field of the inner spherical piezo focusing transducer of 256 elements, and the single focus and multiple are obtained according to different transducer array elements. However, the study uses an integration algorithm, and does not study the influence of nonlinear characteristics on the sound field during high-intensity focused ultrasound propagation. The focus position of the elliptical spherical focusing of three different parameters is simulated. The calculation is based on the equation of state, and the simulation calculation is very large. Generally, the supercomputer can be used for simulation calculation through linear superposition algorithm is using the integral that showed that high sound intensity and medium have great influence on the shape and position of the focal region formed by ultrasonic hifu piezoelectric crystal in 1998, Morita Changji uses ultrasound based on the equations of motion and continuous equations of sound waves.The amount of nonlinear variation in wave propagation is contained in the volume elastic coefficient, which is using acoustic wave propagation velocity, proton velocity.Approximate simulation calculation of degrees and nonlinear coefficients are applied to electromagnetic waves by Yee.The FDTD method of simulation calculation first proposed the three-dimensional nonlinear propagation of high-intensity focused ultrasound. Taking the water experiment of Reicheis in the water body.The high-intensity focused ultrasonic propagation was simulated and the measuring waveform was obtained at the focal point.