Harmonic Beamforming: Performance Analysis and Imaging Results

In this paper, harmonic beamforming (HB), a technique proposed by the authors to improve the quality of tissue-harmonic imaging and contrast-agent imaging processes in medical echography, is briefly presented. It relies on a modification to the delays used in reception beamforming that notably reduces the echoes centered on the fundamental frequency while keeping the echoes centered on the second harmonic and preserving focusing quality. The HB is assessed in terms of its spectral and spatial characteristics, harmonic-to-fundamental ratio (HFR), and range resolution for different bandwidths of the insonifying pulse. The tuning of the parameters involved in HB and its effects are investigated in detail. The results are compared with those provided by traditional methods of harmonic imaging, clearly showing some advantages in the application of the proposed beamforming scheme. Such advantages are also confirmed by analyzing and comparing the results obtained in a simulated contrast-agent imaging task, where HB generated the most similar images to those yielded by the pulse-inversion approach. Therefore, HB is a very promising technique, also considering that it can be very easily incorporated in current ultrasound medical scanners without any hardware modification or frame-rate reduction