Theoretical study of concave spherical ultrasonic and high focused ultrasound for hyperthermia(2)

The maximum sound pressure and the rising temperature is produced by the two sound sources differ greatly, but the ratio of the maximum temperature rise to the maximum sound absorptivity is almost the same.High intensity focused piezoelectric ceramic is indicating that the efficiency of the absorption of sound energy caused by the absorption of sound energy is close to further research: The premise of the same total radiation power Next, the effective treatment area corresponding to the Gauss source is farther away and the lateral range is wider away from the sound source, and the effective treatment area corresponding to the concave spherical self-focusing sound source at the near sound source is slightly deeper and laterally wider.

The effective treatment area is corresponding to the concave spherical self-focusing HIFU piezo element at the near sound source is slightly deeper and laterally wider. When the total effective treatment area of the two is close to the heating time, the difference in rising temperature caused by the two at the sound focus is small，as the heating time increasing, the difference will increase, and the rising temperature is caused by the concave spherical ultrasonic source.When the total radiated power is 10W, the maximum rising temperature is the concave spherical self-focusing source and the focused Gaussian source are .6 23°C and 5 5 °C, respectively. When the focus parameter is changed, the ratio of the maximum temperature is rising to the total radiation power of the hifu piezoelectric crystal will change, but the difference between the two is not large. If the sound absorption rate of the two sound focal points is equal, the concave spherical surface can be obtained. The ratio of the total radiated power and the focused Gaussian source is 0.87, and the corresponding maximum rise ratio of temperature is 10. At this time, the effective treatment areas of the two is close, and the time curves of the two sound focal points will eventually coincide. To maintain the equal sound absorption rates at the geometric focusing of the two sources, the ratio of the maximum rising temperature is corresponding to the ratio of the total radiated power. the concave spherical self-focusing source to the focused Gaussian source is 1 for the maximum rising temperature . 

The key point depends on the maximum sound absorption rate, and the total radiation power is not analyzed by the above,Even if the self-focusing source of concave spherical surface and the focused Gaussian source have the same geometric focal length and acoustic focal spot size, the two places produce the maximum rising temperature position and temperature field. The axial 3dB width of Hifu piezoelectric sensor working is also different.When the vibration speeds of the piezoelectric ceramic sheets of the two focused ultrasound sources are the same, the concave spherical surface can obtain a higher rising temperature from the focusing source, and the focused Gaussian source can control the effective treatment area to a smaller range, and The steady state is reached faster. When the total radiation power is the same, there is a certain difference between the maximum rising temperature values generated by the two, but the rising maximum temperature of the HIFU resonance piezoelectric sensor is the same when the sound absorption rate is the same at the sound focus. Thus, the heating effect of the concave spherical surface from the focusing source and the heating effect of the focused Gaussian source cannot be simply equivalent. In the actual treatment, the effective treatment area of electrical hifu ultrasound piezo can be controlled by changing the vibration velocity value and distribution of the piezoelectric ceramic of the ultrasonic source, thereby ensuring the safety and high efficiency of the treatment.