Nonlinear ultrasonic propagation in biological media

Area of Science:

• Biophysics
• Acoustics
• Materials Science

Background:

• Nonlinearity parameter (B/A) quantifies acoustic nonlinearity in materials.
• Understanding B/A in biological tissues is crucial for medical ultrasound applications.
• Previous studies have explored B/A in various liquids, but data on complex biological materials is limited.

Purpose of the Study:

• To determine the nonlinearity parameter (B/A) for diverse biological materials.
• To investigate the relationship between B/A and concentration in biological solutions.
• To compare B/A values across different biological sample types.

Main Methods:

• Acoustic measurements were performed to determine the amplitude of the second harmonic pressure and the fundamental amplitude.
• The nonlinearity parameter (B/A) was calculated based on these pressure amplitudes.
• Measurements were conducted as a function of distance from the acoustic source.

Main Results:

• Bovine serum albumin and hemoglobin solutions showed a nearly linear increase in B/A with increasing concentration.
• Blood and homogenized liver samples exhibited B/A values comparable to hemoglobin solutions of equivalent dry weight.
• Whole liver tissue demonstrated a higher B/A value than homogenized samples.

Conclusions:

• The nonlinearity parameter (B/A) is concentration-dependent in biological solutions.
• Tissue homogenization affects the acoustic nonlinearity, with whole liver showing greater nonlinearity.
• These findings contribute to the acoustic characterization of biological materials for potential diagnostic applications.