Two-dimensional measurement of the nonlinearity parameter B/A in excised biological samples

Area of Science:

• Acoustics
• Biophysics
• Materials Science

Background:

• Accurate measurement of acoustic nonlinearity parameter (B/A) is crucial for characterizing materials.
• Previous methods were limited in sample size and automation.
• Biological tissue heterogeneity requires high-resolution imaging techniques.

Purpose of the Study:

• To automate and adapt a previously developed B/A measurement technique for small biological samples.
• To develop a two-dimensional imaging method for visualizing B/A distribution in biological tissues.
• To demonstrate the capability of the technique for characterizing tissue structure and variations.

Main Methods:

• Automation of B/A measurement using a LabVIEW program for excised biological samples.
• Lateral shifting of the sound beam focus across a 3 × 3 mm(2) sample area.
• Generation of 2D C-mode images by accumulating 256 measurements with 0.2 mm intervals.

Main Results:

• Successful generation of 2D B/A images for biological samples.
• Demonstration that B/A distribution patterns can differ from linear properties like density and sound speed.
• Visualization of regional variations in B/A within a single biological sample.
• Application to a thermally coagulated biological sample, showcasing utility for small and altered samples.

Conclusions:

• The automated 2D B/A imaging technique provides high-resolution structural information in biological tissues.
• This method reveals detailed acoustic nonlinearity variations, offering insights beyond traditional linear property imaging.
• The technique is effective for small sample volumes and demonstrates potential for various biological and material science applications.