Imaging the nonlinear ultrasonic parameter of a medium.

Area of Science:

• Medical imaging
• Acoustics
• Biophysics

Background:

• The nonlinear ultrasonic parameter B/A quantifies the pressure dependence of ultrasonic velocity.
• This parameter holds potential for characterizing biological and nonbiological media.
• Existing methods for B/A measurement are limited.

Purpose of the Study:

• To develop and demonstrate a novel technique for imaging the nonlinear ultrasonic parameter B/A.
• To generate the first reported images of the nonlinear parameter in biological objects.
• To validate the technique by measuring the nonlinear parameter of water.

Main Methods:

• Utilizing the interaction of two ultrasonic waves: a low-frequency pump wave and a high-frequency probe beam.
• Modulating sound pressure with the pump wave and observing its effect on the probe wave's phase.
• Employing Fourier analysis of phase changes to reconstruct a one-dimensional image of the B/A parameter.
• Scanning the probe beam to obtain a two-dimensional cross-sectional image.

Main Results:

• Successfully generated several cross-sectional images of the nonlinear parameter B/A in biological objects.
• Achieved accurate measurement of the nonlinear parameter of water, consistent with established values.
• Demonstrated the capability to image the spatial distribution of the nonlinear parameter.

Conclusions:

• The developed technique provides the first-ever images of the nonlinear ultrasonic parameter B/A.
• This method offers a promising new tool for material characterization, particularly in biological applications.
• The technique shows potential for non-destructive evaluation and medical diagnostics.