We researched into ultrasound X-wave and field simulation, used high frame rate imaging method based on Fourier transformation to increase resolution and reduce sidelobe of ultrasound images, and applied this technique to the Doppler flow imaging.

The high frame rate pulse-echo imaging method (Fourier method) applies plane wave or limited diffraction array beam to illuminate more area than D&S at one transmit-receive cycle. In this method, a plane wave pulse (broadband) is used in transmission, and limited diffraction beams of different parameters are used in reception. Images are constructed with an inverse Fourier transform after received signals are processed with temporal Fourier transform and nonlinearly mapped into spatial Fourier transform of the object function. Its efficacy has now been proved by one self-built imaging system, and it is further developed to steer plane waves at different angles according to different clinical requirements and coherently sum the object spectrum to increase the imaging quality. The HFR imaging method has a higher lateral image resolution than the D&S imaging method and is less sensitive to phase aberration and noise.

1. Zhaohui Wang, “Resolution, Sidelobe, and Contrast Analysis of Ultrasound Fourier Based High Frame Rate Imaging,” 2020 IEEE International Symposium on Signal Processing and Information Technology, 2020.

2. Zhaohui Wang, “Contrast-resolution Evaluation of Fourier Based High Frame Rate Imaging,” 2020 IEEE Big Data Conference, 2020.

The three-dimensional ultrasound Doppler analysis of the blood flow in a bifurcated blood vessel was simulated. Blood cells are treated as point scatterers randomly distributed in the blood vessel. The blood vessel model is divided into three regions, including the main branch and two subbranches of bifurcation. The velocity and next position of a scatterer (or blood cell) are determined by the laminar flow. The blood flow is simulated by displacing the scatterers between pulse emissions. The axial velocity is estimated using the autocorrelation method on the radio frequency (RF) data simulated by Field II software. A 3D Doppler analysis with angles of rotation of the transducer can accurately rebuild the blood flow direction and the lateral velocity component in each region. This simulation package provides a platform to evaluate the performance of 3-D Doppler imaging methods before the clinical application.

1. Zhaohui Wang, Santosh T. Prakash, “Three-dimensional ultrasound Doppler simulation for vascular bifurcation model,” 2018 IEEE International Symposium on Signal Processing and Information Technology, 2018, pp. 532-535.

2. Jian-yu Lu, Zhaohui Wang, and Sung-Jae Kwon, “Blood flow velocity vector imaging with high frame rate imaging methods,” 2006 IEEE Ultrasonics Symposium Proceedings, 2, 963-966 (2006).

We also developed a few software tools for the research of ultrasound imaging: “Image Display (IMD)” to make the ultrasonic research more convenient; “Carotid Intima-Media Thickness and Plaque Classification (IMTPC)” to the Toledo Hospital for clinical investigation.