Comparison of virtual source synthetic aperture beamforming with an element-based model

Area of Science:

• Medical Imaging
• Acoustics
• Signal Processing

Background:

• Ultrasound beamforming converts backscattered fields into spatial images using propagation models.
• Conventional methods like straight-line propagation cause image degradation (defocusing, reduced SNR, contrast loss) away from the focal point.
• Virtual source methods improve focusing by combining data from multiple transmissions with geometric assumptions.

Purpose of the Study:

• To introduce and evaluate Retrospective Encoding for Conventional Ultrasound Sequences (REFoCUS) beamforming.
• To compare REFoCUS performance against virtual source methods in terms of image quality and signal-to-noise ratio (SNR).

Main Methods:

• REFoCUS models ultrasound transmission as the superposition of individual transducer element responses.
• This approach efficiently estimates the complete dataset of individual element transmit and receive responses.
• Simulations and experimental imaging were used to assess performance.

Main Results:

• REFoCUS isolates individual element contributions, enabling a unified framework for beamforming.
• High-SNR, two-way focused images were achieved from focused plane wave or diverging transmissions.
• No significant differences in SNR or contrast-to-noise ratio were observed between REFoCUS and virtual source methods.

Conclusions:

• REFoCUS provides a robust alternative to virtual source methods for ultrasound beamforming.
• The method effectively enhances image quality by accurately modeling wave propagation.
• REFoCUS demonstrates comparable performance to existing advanced techniques in both simulated and experimental settings.