Categorisation of Microbubble Jets

Abstract

Microbubbles in ultrasound contrast agents have been observed to exhibit ultrasound-induced high-speed liquid-jet formation during bubble collapse nearby boundaries. This phenomena still remains highly unpredictable, and may lead to adverse effects during clinical use of ultrasound in vivo. The purpose of this study was to investigate jetting phenomena in ultrasound contrast agents in an ultrasound field and identify different types of jetting based on factors including jet direction and speed. A total of 425 high-speed videos of commercial ultrasound contrast agents were used for observing, identifying and quantifying ultrasound-induced jetting at 1 MHz ultrasound centre frequency with peak-negative pressures corresponding to 0.2-1.1 MPa. A total of 53 jets were observed and classified into seven types of jetting: bubble-bubble jet towards, bubble jet towards, catapult jet, near-field rigid boundary jet, fuzzy jet, needle-shaped jet and rebound jet, with fuzzy jets being the most prominent type not described in previous literature as its own type. Linear correlation was found between microbubble collapse radius and jet speed. While the occurrence of microbubble jetting remains unpredictable, the types of jetting may be predictable based on vicinity of other bubbles and boundaries.