The assessment of the harmonic response is commonly used in analysis of the signals from ultrasound contrast agents (UCAs). Theoretical and experimental studies report that acoustic behavior of UCAs strongly depends on insonation pressure. Other system parameters, such as the number of cycles, driving and repetition frequency and the pulse shape are equally important. The major focus of this work is to investigate the effect of the shape of driving pulse envelopes on detection of second- (2f), super- (3f, 4f, 5f), sub- (f/2), and ultra-harmonics (3f/2). In this paper, numerical simulations on thin-shelled lipidic UCA have been performed. The simulation results indicate that, high sidelobe suppression envelopes (e.g. 4-term Blackman-Harris), manage to detect second and third harmonic with harmonic-to-fundamental ratio (HFR) of 32 and 69 dB, respectively, at low acoustic pressure of 5 kPa. However, conventional low sidelobe suppression envelopes (e.g. rectangular, cos-tapered, Hanning, Gaussian) fail to identify the harmonic response. Yet the increase of the insonation pressure to 200 kPa leads to increase of the broadband noise. This negatively affects the frequency resolution when high suppression sidelobe envelopes are applied to the driving pulse. As a result, the application of conventional envelopes in harmonic response detection at intermediate acoustic pressure is recommended. It is also worth mentioning, that at high isonation pressure of 0.9 MPa, cos-tapered envelope, having a sidelobe fall-off equal to 18 dB/octave, is able to identify the sub- and ultra-harmonics. In conclusion our study demonstrates that the driving pulse envelope should be selected according to the incident pressure for the complete exploitation of the unique nonlinear signature from UCA. A compromise could be found with the application of adjustable Kaiser-Bessel envelope where by varying the β parameter from 0 to 10 one goes from low to high sidelobe suppression envelope.
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