The acoustic signature of decaying resonant phospholipid microbubbles

Abstract

Sub-capillary sized microbubbles offer improved techniques for diagnosis and therapy of vascular related disease using ultrasound. Their physical interaction with ultrasound remains an active research field that aims to optimize techniques. The aim of this study is to investigate whether controlled microbubble disruption upon exposure to consecutive ultrasound exposures can be achieved. Single lipid-shelled microbubble scattered echoes have been measured in response to two consecutive imaging pulses, using a calibrated micro-acoustic system. The nonlinear evolution of microbubble echoes provides an exact signature above and below primary and secondary resonance, which has been identified using theoretical results based on the Mooney-Rivlin strain softening shell model. Decaying microbubbles follow an irreversible trajectory through the resonance peak, causing the evolution of specific microbubble spectral signatures. The characteristics of the microbubble motion causes varying amounts of shell material to be lost during microbubble decay. Incident ultrasound field parameters can thus accurately manipulate the regulated shedding of shell material, which has applications for both imaging applications and localized drug delivery strategies.

Combined perfusion and doppler imaging using plane-wave nonlinear detection and microbubble contrast agents

“…Phospholipid shells confer stability to microbubbles by reducing the surface tension between the gas core and the liquid, which significantly reduces gas diffusion, particularly if buckling occurs. recent publications [12], [13] indicate that repeated acoustic insonation also causes a slow deflation of phospholipid microbubbles (such as definity), which may be associated with lipid shedding [26], [27]. These phenomena modify the acoustic response from microbubbles over time, which can decorrelate the echo and degrade the doppler signal, but the effect becomes weaker as the acoustic driving pulse pressures and pulse durations are reduced.…”

Experimental study of light emitted by spark-generated bubbles in water

“…Bubble oscillations have long been an important topic in fluid dynamics. While they have been traditionally associated with erosion damage [1,2], recent efforts have been aimed at medical applications, such as contrastenhancing in ultrasonic imaging [3][4][5][6], ultrasound therapy monitoring [7], and shock wave lithotripsy [8]. In experimental studies of free bubble oscillations both spark-generated bubbles [9][10][11] and laser-generated bubbles [12] represent very useful tools.…”

The Time Difference in Emission of Light and Pressure Pulses From Oscillating Bubbles

“…Bubble oscillations have long been an important topic in fluid dynamics. While they have traditionally been studied in connection with erosion damage [1], recent efforts have been aimed at medical applications such as contrast-enhancing in ultrasonic imaging [2][3][4][5][6][7]. Physical processes in oscillating bubbles are very complex and so far many points in this field have not yet been clarified.…”