Baseband delay multiply and sum beamformer for three-dimensional ultrasound localization microscopy

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Ultrasound Technology

Background:

• Three-dimensional ultrasound localization microscopy (3D ULM) offers super-resolution volumetric microvascular imaging.
• Matrix array implementations face limitations in effective aperture and sensitivity, degrading imaging quality and microbubble tracking.

Purpose of the Study:

• To present a baseband delay-multiply-and-sum (DMAS) beamformer for 3D ULM.
• To develop a computationally efficient implementation of DMAS for 1024-element matrix arrays.
• To evaluate DMAS performance against conventional beamformers (DAS, CF, SACF) in simulations, phantoms, and in vivo imaging.

Main Methods:

• Development and implementation of a baseband delay-multiply-and-sum (DMAS) beamformer.
• Comparative analysis using simulations, phantom experiments, and in vivo rat brain imaging.
• Evaluation metrics included point spread function (PSF), Fourier shell correlation (FSC), microbubble (MB) trajectory counts, and vascular saturation.

Main Results:

• DMAS demonstrated superior volumetric ULM reconstructions compared to DAS, CF, and SACF.
• DMAS achieved higher effective spatial resolution (via FSC) and significantly increased MB trajectory counts (up to 3.07 million).
• DMAS resulted in approximately twofold higher vascular saturation, indicating faster and more complete microvascular depiction, with a 370x computational speedup.

Conclusions:

• Baseband DMAS is a robust and computationally efficient beamforming strategy for 3D ULM.
• DMAS enhances microvascular tracking and imaging completeness, outperforming traditional methods.
• Point spread function (PSF) metrics alone may not fully predict final 3D ULM reconstruction quality.