Synthetic Aperture Focusing for Multi-Covariate Imaging of Sub-Resolution Targets.

Area of Science:

• Ultrasound imaging
• Medical imaging physics
• Signal processing

Background:

• Coherence-based ultrasound imaging methods struggle with image quality degradation beyond the focal depth.
• Synthetic aperture techniques improve image depth of field by combining data from multiple transmissions.
• Multi-covariate Imaging of Sub-resolution Targets (MIST) offers improved image quality for diffuse targets but has limited depth of field.

Purpose of the Study:

• To apply synthetic aperture focusing to MIST to overcome depth of field limitations.
• To evaluate the performance of synthetic aperture MIST across different ultrasound transmit geometries.
• To assess the effectiveness of synthetic aperture MIST in simulation, phantom, and in vivo studies.

Main Methods:

• Synthetic aperture focusing was applied to the MIST imaging method.
• Evaluations were conducted using focused, plane-wave, and diverging-wave transmit geometries.
• Performance was assessed by comparing contrast-to-noise ratio (CNR) with conventional MIST and synthetic aperture B-Mode.

Main Results:

• Synthetic aperture MIST demonstrated consistent CNR improvements over dynamic receive MIST outside the transmit depth of field.
• In vivo results showed significant improvements in contrast (16.8 dB) and CNR (16.6%) over dynamic receive MIST.
• Synthetic aperture MIST also outperformed synthetic aperture B-Mode, with improvements of 17.4 dB in contrast and 32.3% in CNR.

Conclusions:

• Synthetic aperture focusing effectively enhances MIST performance, extending its usable depth of field.
• The method shows consistent improvements across various synthetic transmit strategies.
• Synthetic aperture MIST is broadly applicable and offers significant advantages for ultrasound imaging of diffuse targets.