Volumetric ultrasound via 3D Null Subtraction Imaging with matrix array

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Signal Processing

Background:

• Conventional ultrasound imaging faces limitations in resolution and speed for dynamic applications.
• Matrix arrays offer advanced capabilities but require efficient beamforming methods.
• Null-subtraction techniques traditionally applied in 2D imaging need extension for volumetric data.

Purpose of the Study:

• To introduce and validate a three-dimensional Null Subtraction Imaging (3D NSI) framework for matrix array ultrasound.
• To enable simultaneous synthetic beam narrowing and sidelobe suppression in both azimuthal and elevational dimensions.
• To improve image resolution, contrast, and acquisition speed for real-time 4D ultrasound.

Main Methods:

• Developed specialized NSI apodizations for 2D receive apertures within a nonlinear beamforming framework.
• Implemented a spiral no-reuse apodization for efficient transmit-receive event management.
• Evaluated the framework using computer simulations, tissue-mimicking phantoms, and in vivo carotid imaging.

Main Results:

• Achieved significant improvements in azimuthal and elevational resolutions (average 36%) and contrast ratio (approx. 20%) compared to Delay-and-Sum (DAS).
• Demonstrated up to a 16-fold increase in acquisition volume rate using sparse apertures and spiral no-reuse apodization.
• Attained acquisition rates exceeding 1000 volumes per second with a manageable computational load.

Conclusions:

• 3D NSI is a versatile and efficient beamforming method for matrix arrays, outperforming conventional DAS.
• The framework significantly enhances resolution, contrast, and acquisition speed, making it suitable for real-time 4D imaging.
• 3D NSI shows strong potential for advancing cardiovascular and other dynamic ultrasound applications.