Synthetic-focusing strategies for real-time annular-array imaging

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Acoustics

Background:

• Annular arrays offer enhanced image quality with fewer elements.
• Synthetic-focusing (SF) strategies improve ultrasound imaging without specialized electronics by beamforming individual transmit-to-receive (TR) pairs.

Purpose of the Study:

• To evaluate synthetic-focusing (SF) strategies with high-frequency ultrasound annular arrays.
• To compare acoustic field simulations with experimental data for 18 and 38 MHz arrays.
• To assess the impact of removing outer receive channels on image quality metrics.

Main Methods:

• Simulated and experimentally acquired acoustic field data from wire and anechoic-sphere phantoms.
• Utilized five-element annular arrays operating at 18 and 38 MHz.
• Acquired data for all 25 TR combinations, processed with full SF and reduced SF (outer channels removed).

Main Results:

• Removing outer receive channels degraded lateral resolution and signal-to-noise ratio (SNR).
• Depth of field (DOF) was not reduced, though its amplitude decreased.
• Contrast-to-noise ratio (CNR) remained above 1 and relatively constant with depth.
• Simulated and measured quantities showed nearly identical relative changes for both frequencies.

Conclusions:

• Full synthetic-focusing (SF) with all transmit-receive (TR) pairs provides optimal image quality for high-frequency annular arrays.
• Reduced TR-pair approaches offer minimal qualitative differences in B-mode images but impact quantitative metrics.
• SF strategies are effective for enhancing image quality in high-frequency ultrasound applications.