Virtual Source-Based Apodization for Diverging Wave Imaging: An Experimental Study

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Signal Processing

Background:

• Ultrafast imaging techniques, including diverging wave imaging (DWI), enable high frame rates for advanced medical diagnostics like Doppler imaging and shear wave elastography.
• Conventional transmit apodization is not feasible in ultrafast imaging due to synthetic beam formation during coherent compounding.
• Optimizing transmit apodization weights for DWI, unlike plane wave imaging (PWI), has remained an underexplored area.

Purpose of the Study:

• To present the real-time implementation of a previously developed closed-form approach for mapping synthetic aperture imaging (SAI) apodization weights to compound masks for DWI.
• To validate the efficacy of this compound mask approach across various virtual source (VS) configurations and ultrasound array geometries.

Main Methods:

• A closed-form approach was adapted to map SAI apodization weights to compound phase weights for DWI, termed a compound mask.
• The compound mask method was implemented in real-time on a Verasonics ultrasound scanner.
• Validation was performed using linear, curvilinear, and tilted virtual source distributions with linear and convex arrays.

Main Results:

• The real-time implementation successfully applied the compound mask across all tested virtual source configurations.
• Experimental results demonstrated significant improvements in B-mode image quality for both linear and convex arrays.
• The compound mask approach did not compromise the real-time performance of the ultrafast imaging system.

Conclusions:

• The compound mask method provides an effective means to optimize transmit apodization in diverging wave imaging.
• This technique enhances image quality in ultrafast ultrasound diagnostics without performance degradation.
• The approach is versatile, applicable to various virtual source arrangements and array types.