Influence of the pressure-dependent resonance frequency on the bifurcation structure and backscattered pressure of ultrasound contrast agents: a numerical investigation

Abstract

The bifurcation structure of the oscillations of ultrasound contrast agents (UCAs) was studied as a function of the driving pressure for excitation frequencies that were determined using the UCAs pressuredependent resonances ( f s ). It was shown that when excited by the ( f s ), the UCA can undergo a saddlenode bifurcation (SNB) to higher amplitude oscillations. The driving pressure at which the SNB occurs is controllable and depends on the ( f s ) magnitude. Utilizing the appropriate ( f s ), the scattering cross section of the UCAs can significantly be enhanced (e.g., ∼ninefold) while at the same time avoiding potential UCA destruction (by limiting the radial expansion ratio <2). This offers significant advantages for optimizing UCA-mediated imaging and therapeutic ultrasound applications.

Nonlinear power loss in the oscillations of coated and uncoated bubbles: Role of thermal, radiation and encapsulating shell damping at various excitation pressures

“…3g shows that SH resonance peak appears at f =≈ 2f r . Rd becomes the major damping factor at frequencies below f r ; however, due to the fact that Rmax R 0 have exceeded 2 the bubble can not sustain long lasting stable oscillations and will undergo destruction [24,59]. We observe the same phenomenon in the C3F8 gas core bubbles ( Fig.…”

“…Morever, the damping predicted by LTM and FTM are ≈ 30% higher than the predictions of the NTM models. At higher pressure the total dissipated power grows at resonance and the 2nd SuH resonance while both resonance frequencies decrease in magnitude; this is a phenomenon known as pressure dependent (PD) resonance [24]. We also observe the generation of a third peak below 2nd SuH resonance which indicates the 3rd SuH resonance frequency.…”

“…An increase in pressure leads to increase in the STDR. The STDR is very high at P Df r [24] (e.g. 0.4 at 100 kPa).…”

“…Dynamics of the acoustically excited bubbles are nonlinear and chaotic. These dynamics have been the subject of numerous experimental [1,15,[17][18][19][20] and numerical [21][22][23][24][25][26][27][28][29][30] studies . Achieving the full potential of bubbles in applications and understanding their role in the associated phenomena not only requires a detailed knowledge over their complex behavior but also on the effect of bubble oscillations on the propagation of acoustic waves.…”

Classification of the bifurcation structure of a periodically driven gas bubble

“…The accumulated knowledge of this nonlinear behavior has been summarized in many reviews [18][19][20] and papers [1,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. The most important findings are the existence of period-doubling cascades in the bifurcation structure [1,21,30,31,35], the appearance of resonance horns in the amplitude-frequency plane of the driving [24,27,34] or the alternation of chaotic and periodic windows [21,23,33].…”