“…In addition, comparing the two cases without and with considering the inter-bubble interaction exhibits obvious increases of the differences in both X max and R res as the ultrasound pressure increases. The presented evidence reveals that the influences of the inter-bubble interaction on both bubble oscillation amplitude and resonant radius are amplified at a higher acoustic pressure, due to a stronger inter-bubble interaction with the acoustic pressure increasing as demonstrated in previous studies [31] , [34] , [37] , [40] . Fig.…”
Section: Resultssupporting
confidence: 78%
“…Similar to the case of a single bubble, extensive numerical research has been devoted to the dynamics of the multi-bubble system, including the radial oscillation [28] , [29] , [30] , translation motion [31] , [32] , bubble deformation [33] , resonance frequency [34] , and the secondary Bjerknes force [35] , [36] for two oscillating bubbles in water, or the radial oscillation and/or translation motion of two interacting bubbles in viscoelastic media [37] , [38] , [39] , [40] , as well as the radial oscillation and resonance characteristics of multiple bubbles in water [41] , [42] , [43] , [44] , etc . The results showed that the inter-bubble interaction can significantly affect the bubble dynamic behaviors, such as enhancing/suppressing oscillation amplitude [28] , [30] , [37] , [44] , forcing translation motion of two bubbles close to/away from each other [35] , [36] , [37] and left shifting the resonance frequency [28] , [34] , etc . Moreover, it also demonstrated that the inter-bubble interaction highly depends on the ultrasound parameters, the initial bubble radii, the distances between bubbles, the number of bubbles and the medium viscoelasticity [28] , [37] , [39] , [40] , [44] .…”
“…In addition, comparing the two cases without and with considering the inter-bubble interaction exhibits obvious increases of the differences in both X max and R res as the ultrasound pressure increases. The presented evidence reveals that the influences of the inter-bubble interaction on both bubble oscillation amplitude and resonant radius are amplified at a higher acoustic pressure, due to a stronger inter-bubble interaction with the acoustic pressure increasing as demonstrated in previous studies [31] , [34] , [37] , [40] . Fig.…”
Section: Resultssupporting
confidence: 78%
“…Similar to the case of a single bubble, extensive numerical research has been devoted to the dynamics of the multi-bubble system, including the radial oscillation [28] , [29] , [30] , translation motion [31] , [32] , bubble deformation [33] , resonance frequency [34] , and the secondary Bjerknes force [35] , [36] for two oscillating bubbles in water, or the radial oscillation and/or translation motion of two interacting bubbles in viscoelastic media [37] , [38] , [39] , [40] , as well as the radial oscillation and resonance characteristics of multiple bubbles in water [41] , [42] , [43] , [44] , etc . The results showed that the inter-bubble interaction can significantly affect the bubble dynamic behaviors, such as enhancing/suppressing oscillation amplitude [28] , [30] , [37] , [44] , forcing translation motion of two bubbles close to/away from each other [35] , [36] , [37] and left shifting the resonance frequency [28] , [34] , etc . Moreover, it also demonstrated that the inter-bubble interaction highly depends on the ultrasound parameters, the initial bubble radii, the distances between bubbles, the number of bubbles and the medium viscoelasticity [28] , [37] , [39] , [40] , [44] .…”
“…It allows the indirect observation of vessels through intravascular microbubbles. The injected bubbles of air or perfluorocarbon increase the intensity of blood vessels by more than a factor of a hundred even in small concentrations (in the order of 1 per 105 red blood cells) due to impedance mismatch between blood and gas [137] , [138] . Ultrasound localization microscopy (ULM) is an emerging technique providing impressive super-resolved images of microvasculature, i.e.…”
Section: Ultrasound Probes For In-vivo Imagingmentioning
“…To date, this has been addressed by increasing the concentration of MBs injected and hence generating more MB signals per imaging frame (Christensen-Jeffries et al 2019). Higher concentrations, however, mean that MBs will be closer to each other, which makes it more challenging to isolate them, especially as the MB signals may generate coherent interfere patterns in the image, or, at closer distance, their oscillations may start to interfere with each other (Yusefi and Helfield 2022). The radiated acoustic signals from MBs start to interfere when the MBs approach each other and their point spread function (PSF) starts to overlap in space.…”
Super-Resolution Ultrasound (SRUS) through localising and tracking of Microbubbles (MBs) can achieve sub-wavelength resolution for imaging microvascular structure and flow dynamics in deep tissue in-vivo. The technique assumes that signals from individual MBs can be isolated and localised accurately, but this assumption starts to break down when the MB concentration increases and the signals from neighbouring MBs start to interfere. The aim of this study is to gain understanding of the effect of MB-MB distance on ultrasound images and their localisation. Ultrasound images of two MBs approaching each other were synthesised by simulating both ultrasound field propagation and nonlinear MB dynamics. Besides the distance between MBs, a range of other influencing factors including MB size, ultrasound frequency, transmit pulse sequence, pulse amplitude and localisation methods were studied. The results show that as two MBs approach each other, the interference fringes can lead to significant and oscillating localisation errors, which are affected by both the MB and imaging parameters. When modelling a clinical linear array probe operating at 6MHz, localisation errors between 20 to 30 µm (∼1/10th wavelength) can be generated when MBs are ∼ 500µm (2 wavelengths or ∼ 1.7 times the Point Spread Function (PSF)) away from each other. When modelling a cardiac probe operating at 1.5 MHz, the localisation errors were as high as 200 µm (∼1/5th wavelength) even when the MBs were more than 10 wavelengths apart (2.9 times the PSF). For both frequencies, at smaller separation distances, the two MBs were misinterpreted as one MB located in between the two true positions. Cross-correlation or Gaussian fitting methods were found to generate slightly smaller localisation errors than centroiding. In conclusion, caution should be taken when generating and interpreting SRUS images obtained using high agent concentration with MBs separated by less than 1.7 to 3 times the PSF, as significant localisation errors can be generated due to interference between neighbouring MBs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
