Ultrasound harmonic imaging with reducing speckle noise by an interlaced iterative frequency compounding approach

Speckle noise is a phenomenon inherent in any coherent imaging system and decreases the signal-to-noise ratio (SNR), which brings down the imaging quality. Speckle noise reduction is particularly important in the tissue harmonic imaging (THI) since it has the lower energy and the poorer SNR than the fundamental imaging (FI). Speckle can be reduced by frequency compounding (FC), which means incoherently averaging the images with different speckle patterns acquired by changing the center frequency of the pulse. As for the THI, the difference in the emission spectrum doubles when using the FC. In this paper, we propose an interlaced iterative frequency compounding (IIFC) method with the pulse inversion (PI) technique. The new method brings a good speckle suppression performance while the high frame rate is retained. To illustrate the performance of our method, experiments have been conducted on the simulated data. A nonlinear simulation platform based on the full-wave model is used in the harmonic imaging simulation. Results show that our method brings the SNR an improvement of up to 22% in comparison with the single frame THI while maintaining a far better performance in both terms of resolution and contrast than the FI. We also demonstrate that our method for THI retains the high frame rate although using PI.