Comparison of 3D Synthetic Aperture Imaging and Explososcan using Phantom Measurements

In this paper, initial 3D ultrasound measurements from a 1024 channel system are presented. Measurements of 3D Synthetic aperture imaging (SAI) and Explososcan are presented and compared. Explososcan is the ’gold standard’ for real-time 3D medical ultrasound imaging. SAI is compared to Explososcan by using tissue and wire phantom measurements.

The measurements are carried out using a 1024 element 2D transducer and the 1024 channel experimental ultrasound scanner SARUS. To make a fair comparison, the two imaging techniques use the same number of active channels, the same number of emissions per frame, and they emit the same amount of energy per frame.

The measurements were performed with parameters similar to standard cardiac imaging, with 256 emissions to image a volume spanning 90×90 and 150mm in depth. This results in a frame rate of 20 Hz. The number of active channels is set to 316 from the design of Explososcan. From wire phantom measurements the point spread functions of both techniques were measured.

At 40mm depth Explososcan achieves a main lobe width (FWHM) of 2.5mm while SAI’s FWHM is 2.2 mm. At 80mm the FWHM is 5.2mm for Explososcan and 3.4mm for SAI, which is a difference of 35 %. Another metric used on the PSF is the cystic resolution, which expresses the ability to detect anechoic cysts in a uniform scattering media.

SAI improved the cystic resolution, R20dB, at 40mm depth from 4.5mm to 1.7mm and at 80mm from 8.2mm to 2.8 mm, compared to Explososcan. The speckle pattern looked better for SAI compared to Explososcan’s spatial shift variant speckle pattern.