2019 年 85 巻 876 号 p. 19-00152
The purpose of this study is to obtain better physical understandings of the theoretical thresholds of the insonation acoustic pressure amplitudes for medical diagnostic ultrasound applications. For this purpose, a physical model in terms of non-linear resonance of single bubble volumetric oscillations has been developed, to reproduce the threshold insonation acoustic pressure amplitudes that are numerical solutions of Gilmore's equation. It is confirmed, under the condition of the adiabatic state change of the in-bubble gas with a maximum temperature of 5000 K, the present model well-reproduces the influences of the insonation center frequency, the liquid viscosity and surface tension in a range of 0.5 to 16 MHz, 0.0 to 8.0 mPa･s, and 30 to 70 mN/s, respectively, on the threshold insonation acoustic pressure amplitudes. Based on this model, a dimensionless physical index of the insonation acoustic pressure amplitude with a threshold value and a set of fundamental dimensionless parameters constituting that index are defined.
