Ultrasound Autofocusing: Common Midpoint Phase Error Optimization via Differentiable Beamforming.

Area of Science:

• Medical Imaging
• Acoustics
• Wave Propagation

Background:

• Heterogeneous media in ultrasound imaging cause phase aberrations, degrading image resolution and contrast.
• Adaptive imaging techniques aim to correct these aberrations for better focusing.

Purpose of the Study:

• To propose a novel autofocusing paradigm for aberration correction in ultrasound imaging.
• To utilize common midpoint phase error (CMPE) for robust aberration measurement and acoustic autofocusing.

Main Methods:

• Fitting an acoustic velocity field to pressure measurements via CMPE optimization.
• Employing a straight-ray wave propagation model for beamforming in diffusely scattering media.
• Iterative optimization using a differentiable beamforming approach for simultaneous focus improvement and velocity field estimation.

Main Results:

• Common midpoint phase error (CMPE) is a robust measure of phase aberration for acoustic autofocusing.
• The method successfully estimates the acoustic velocity field of the interrogated medium.
• Demonstrated performance in silico, in vitro, and in vivo models.

Conclusions:

• The proposed method offers practical applications in distributed aberration quantification, correction, and velocity estimation for medical ultrasound autofocusing.
• This approach enables improved image focus and accurate velocity field mapping without explicit numerical time-stepping models.