Broadband minimum variance beamforming for ultrasound imaging

Area of Science:

• Ultrasound imaging
• Medical imaging signal processing
• Beamforming algorithms

Background:

• Near-field beamforming is crucial for high-resolution ultrasound.
• Traditional delay-and-sum (DS) beamformers have limitations in achieving optimal lateral resolution.
• Broadband data processing requires advanced techniques for accurate imaging.

Purpose of the Study:

• To propose and evaluate a minimum variance (MV) beamforming approach for broadband ultrasound data.
• To compare the performance of the MV beamformer against conventional DS beamformers.
• To assess the impact of steering vector errors on the robustness of the MV beamformer.

Main Methods:

• A frequency-domain minimum variance (MV) beamforming approach was developed.
• The MV beamformer utilizes adapted, complex apodization weights for each frequency subband.
• Simulations using Field II software were performed with various targets and emissions, comparing MV with DS (boxcar and Hanning weights).

Main Results:

• The MV beamformer demonstrated a significant increase in lateral resolution (reduced FWHM) and improved contrast compared to DS methods.
• Even with a single emission, MV beamforming achieved superior resolution (0.08 mm FWHM) versus DS (0.79-1.33 mm FWHM).
• The MV beamformer showed reduced robustness to steering vector errors (sound speed estimation errors) compared to DS beamformers, though DS did not outperform MV.

Conclusions:

• The proposed frequency subband MV beamformer offers a substantial improvement in lateral resolution for ultrasound imaging.
• The MV approach provides enhanced performance even with limited emissions, making it efficient for broadband data.
• While sensitivity to steering vector errors exists, the MV beamformer's superior resolution makes it a promising technique for advanced ultrasound applications.