Comparison of 3-D Synthetic Aperture Phased-Array Ultrasound Imaging and Parallel Beamforming

This paper demonstrates that synthetic apertureimaging (SAI) can be used to achieve real-time 3-D ultra-sound phased-array imaging. It investigates whether SAI in-creases the image quality compared with the parallel beam-forming (PB) technique for real-time 3-D imaging. Data areobtained using both simulations and measurements with anultrasound research scanner and a commercially available 3.5-MHz 1024-element 2-D transducer array.

To limit the probecable thickness, 256 active elements are used in transmit andreceive for both techniques. The two imaging techniques weredesigned for cardiac imaging, which requires sequences de-signed for imaging down to 15cm of depth and a frame rateof at least 20Hz. The imaging quality of the two techniquesis investigated through simulations as a function of depth andangle.

SAI improved the full-width at half-maximum (FWHM) at low steering angles by 35%, and the 20-dB cystic resolutionby up to 62%. The FWHM of the measured line spread func-tion (LSF) at 80mm depth showed a difference of 20% in favorof SAI. SAI reduced the cyst radius at 60mm depth by 39%in measurements.

SAI improved the contrast-to-noise ratiomeasured on anechoic cysts embedded in a tissue-mimickingmaterial by 29% at 70mm depth. The estimated penetrationdepth on the same tissue-mimicking phantom shows that SAIincreased the penetration by 24% compared with PB. NeitherSAI nor PB achieved the design goal of 15cm penetrationdepth.

This is likely due to the limited transducer surface areaand a low SNR of the experimental scanner used.