Frequency-sum beamforming for passive cavitation imaging

Area of Science:

• Acoustics
• Signal Processing
• Medical Imaging

Background:

• Beamforming uses spatial filtering for sound source localization from sensor array data.
• Resolution is affected by acoustic frequency, array geometry, and target location.
• Medium scattering degrades beamforming resolution, especially at higher frequencies.

Purpose of the Study:

• Evaluate frequency-sum (FS) beamforming for enhanced resolution and reduced scattering sensitivity.
• Compare FS beamforming with conventional delay-and-sum (DAS) and minimum variance (MV) methods.
• Assess performance using simulations and passive cavitation imaging.

Main Methods:

• FS beamforming utilizes a quadratic product of complex signal amplitudes to generate higher frequency information from lower frequency components.
• Data-dependent (MV) or data-independent (DAS) weight vectors were employed.
• Simulations and experiments used a 128-element linear array recording 3 MHz and 6 MHz emissions.

Main Results:

• FS beamforming yielded a smaller point spread function (PSF) compared to conventional DAS beamforming.
• FS beamforming exhibited less computation time than MV beamforming.
• Performance was evaluated in free space and mild scattering conditions using metrics like PSF size, contrast, and computation time.

Conclusions:

• FS beamforming enhances resolution and reduces scattering sensitivity in sound source localization.
• It offers advantages in PSF size and computation time over DAS and MV beamforming, respectively.
• A limitation of FS beamforming is its potential failure in the presence of multiple unknown sound sources.