Influences of liquid viscosity and surface tension on the theoretical threshold value of the mechanical index

Abstract

Numerical simulations of single bubble volumetric oscillations have been conducted by using Gilmore model (Gilmore, 1952), to study the influences of liquid viscosity and surface tension on the theoretical threshold value (MI_t) of the mechanical index (MI) that has been successfully used for the safe application of diagnostic ultrasound. MI_t is defined as the minimum value of MI at various bubble radii and ultrasound frequencies when the temperature inside a bubble reaches 5000 K. The results show that MI_ts for water and blood are 0.314 and 0.405, respectively. It is found that the greater the viscosity or the surface tension is, the greater MI_t is. It is also found that the ultrasound center frequency that gives MI_t has a negative correlation to the viscosity and surface tension.