Coherent array imaging using phased subarrays. Part II: simulations and experimental results

Area of Science:

• Ultrasound Imaging
• Medical Imaging Technology
• Array Signal Processing

Background:

• Phased subarray (PSA) imaging presents a hardware channel reduction strategy between classical synthetic aperture (CSA) and full-phased array (FPA) imaging.
• PSA performance is typically intermediate to CSA and FPA, contingent on the degree of hardware simplification.

Purpose of the Study:

• To evaluate the performance of PSA imaging by comparing it with CSA and FPA imaging techniques.
• To investigate the impact of hardware complexity reduction on imaging performance using simulated and experimental data.

Main Methods:

• Simulated and experimental data from a 3-MHz, 128-element capacitive micromachined ultrasound transducer (CMUT) array were used for FPA, CSA, and PSA imaging of a resolution phantom.
• System point responses were analyzed in spatial and frequency domains to study effects of signal bandwidth, filter size, and subsampling rate on PSA performance.
• Sector-scanned images were reconstructed using wideband experimental data, employing seven 32-element subarrays for PSA imaging.

Main Results:

• PSA imaging demonstrated a 10% improvement in 6-dB lateral resolution at the transmit focal zone compared to FPA.
• Axial point resolution in PSA imaging was found to be identical to that of FPA imaging.
• PSA imaging resulted in a signal-to-noise ratio (SNR) 4.9 dB lower than FPA (58.3 dB total) and a 10% reduction in contrast-to-noise ratio (CNR).

Conclusions:

• PSA imaging offers a flexible approach to ultrasound imaging, allowing for a trade-off between SNR and frame rate for simplified front-end hardware.
• The study validates theoretical expectations for PSA imaging performance through simulated and experimental results.
• PSA imaging provides a viable method for reducing hardware complexity while maintaining competitive image resolution.