A new theoretical equation was discovered by researchers from the University of Tsukuba for ultrasonic wave propagation through encapsulated bubble-filled liquids. They discovered that accurately predicting the behavior of sound waves required including the bubble shell’s compressibility. Based on the creation of improved contrast agents, this work may result in improved ultrasound imaging resolution.
Because it can provide doctors with detailed diagnostic images in a safe and non-invasive manner, ultrasound has evolved into an essential component of modern healthcare. The technology works by sending high-frequency sound waves through a transducer and listening for echoes at the interface of different densities of tissues.
In light of the time it takes for the reverberations to return, the PC can reproduce the picture. Contrast agents like microbubbles are used for echocardiograms and liver scans due to ultrasound’s low resolution, which is one of its major drawbacks. To create better contrast agents, a deeper theoretical comprehension of the physics of the interaction between sound waves and encapsulated microbubbles with a thick shell is still required.
“Our decision to model the shell as a viscoelastic object proved to be crucial to the investigation.”
Professor Tetsuya Kanagawa says.
Now, researchers at the University of Tsukuba have developed brand-new nonlinear equations that can be applied to multiple bubbles and take into account the shell layer’s compressibility. “Because previous research did not model realistic properties for the bubble surface, the researchers chose this path.” According to the author, Professor Tetsuya Kanagawa, “We modeled the shell as a viscoelastic object, which turned out to be an important factor in the analysis.”
Compressibility estimates the overall change in volume of a liquid or solid in light of an increment or decline in pressure. The bubble itself was largely ignored in other research projects, which tended to concentrate on the bubble’s interior deformations. The inclusion of the shell in the calculations increased the attenuation (dissipation) coefficient, according to the researchers.
According to Professor Kanagawa, “our work helps pave the way for future refinements to the theory of sound attenuation in liquids.” This project’s microbubbles could also be used for therapeutic purposes, like targeted drug delivery. All things considered, sound waves could make the air pockets burst at specific times or areas in the body, delivering the medication.
Physics of Fluids is the journal that published the work.
More information: Tetsuya Kanagawa et al, Nonlinear acoustic theory on flowing liquid containing multiple microbubbles coated by a compressible visco-elastic shell: Low and high frequency cases, Physics of Fluids (2022). DOI: 10.1063/5.0101219
