Range side lobe inversion for chirp-encoded dual-band tissue harmonic imaging [Correspondence]

Abstract

Dual-band (DB) harmonic imaging is performed by transmitting and receiving at both fundamental band (f0) and second-harmonic band (2f0). In our previous work, particular chirp excitation has been developed to increase the signal- to-noise ratio in DB harmonic imaging. However, spectral overlap between the second-order DB harmonic signals results in range side lobes in the pulse compression. In this study, a novel range side lobe inversion (RSI) method is developed to alleviate the level of range side lobes from spectral overlap. The method is implemented by firing an auxiliary chirp to change the polarity of the range side lobes so that the range side lobes can be suppressed in the combination of the original chirp and the auxiliary chirp. Hydrophone measurements show that the RSI method reduces the range side lobe level (RSLL) and thus increases the quality of pulse compression in DB harmonic imaging. With the signal bandwidth of 60%, the RSLL decreases from -23 dB to -36 dB and the corresponding compression quality improves from 78% to 94%. B-mode images also indicate that the magnitude of range side lobe is suppressed by 7 dB when the RSI method is applied.

Supplementary Golay pair for range side lobe suppression in dual-frequency tissue harmonic imaging

“…Both the side lobe and the main lobe have the amplitude of À2. Besides the range side lobe generated from the DC and 3f 0 interferences, the mutual cross-talk between the f 0 and 2f 0 harmonic signals may also produce range side lobes [17]. Both sources of range side lobes should be considered in the design of the supplementary Golay excitation.…”