Nonlinear Ultrasound Propagation in Homogeneous and Heterogeneous Media: Factors Affecting the in situ Mechanical Index (MI)

This study used 3D nonlinear ultrasound simulations to identify the sources of error when estimating the in situ Peak Rarefaction Pressure (PRP) as compared to linear derating in the context of the Mechanical Index (MI) measurement. We found that varying material nonlinearity within the range of soft tissue (5 <; B/A <; 10) does not affect PRP estimation. We also found that for large apertures (F/1.5), phase aberration is the dominant factor that causes the linear derating MI method to consistently report higher PRP than actually occurs in situ. For smaller apertures (F/5), both phase aberration and reverberation clutter cause the linear derating MI method to report lower PRP than actually occurs in situ.