Examining the propagation of ultrasonic waves through liquids that contain encapsulated bubbles, researchers from the University of Tsukuba have made an intriguing discovery. They have found that accurately predicting the behavior of sound waves requires the consideration of the compressibility of the bubble shell. This novel theoretical equation, developed by the researchers, holds significant potential for enhancing ultrasonic imaging resolution by advancing the creation of improved contrast agents.
Due to its ability to safely and non-invasively give clinicians detailed diagnostic images, ultrasound has become a crucial tool in contemporary healthcare. The method involves using a transducer to transmit high-frequency sound waves, then listening for the echoes that are produced at the junction between tissues with various densities.
Examining the propagation of ultrasonic waves
The computer can rebuild the image by measuring how long it takes for the echoes to come back. However, one of the main limitations of ultrasound is its lack of resolution, which necessitates the introduction of contrast agents, such as microbubbles, for liver scans or echocardiograms. To develop superior contrast agents, further research is still required to fully understand the physics of the interaction between encapsulated microbubbles, which have a thick shell, and sound waves.
In order to expand its application to many bubbles, researchers at the University of Tsukuba have now developed new nonlinear equations that account for the compressibility of the shell layer. Because earlier studies did not model the actual qualities of the bubble surface, the researchers took this course. “We modeled the shell as a viscoelastic object, which turned out to be an important factor in the analysis,” adds author Professor Tetsuya Kanagawa.
The relative volume change that a fluid or solid experiences in response to an alteration in pressure is measured by compressibility. Other studies frequently neglected the bubble itself in favor of concentrating on internal deformations. The scientists discovered that adding the shell to the computations has the effect of increasing the attenuation (dissipation) coefficient.
According to Professor Kanagawa, “Our work paves the way for further development of the theory of sound attenuation in liquids.” The microbubbles investigated in this project may also be used for therapeutic purposes, such as the delivery of certain drugs. Then, at particular times or locations in the body, sound waves can induce the bubbles to break, delivering the medicine.
In conclusion, examining the propagation of ultrasonic waves through liquids containing encapsulated bubbles reveals several key findings and implications. Firstly, when ultrasonic waves pass through a liquid containing encapsulated bubbles, the bubbles can significantly affect the transmission of the waves. The interaction between the waves and the bubbles depends on various factors such as the size, shape, and concentration of the bubbles, as well as the properties of the liquid itself.
One important observation is that the presence of bubbles can cause scattering and attenuation of the ultrasonic waves. As the waves encounter the bubbles, they are scattered in different directions, leading to a loss of energy and a decrease in wave intensity. This scattering effect is more pronounced when the size of the bubbles is comparable to the wavelength of the ultrasonic waves.
Furthermore, the bubbles can also act as reflectors, bouncing the waves back in the opposite direction. This phenomenon, known as acoustic reflection, can be exploited in medical imaging techniques like ultrasound imaging, where the reflected waves provide information about the internal structures of the body. The behavior of the bubbles also depends on their stability and the surrounding liquid. For example, if the bubbles are unstable or have a tendency to collapse, they can generate transient shock waves that further affect the propagation of ultrasonic waves.
This behavior is particularly important in the field of cavitation, where the controlled formation and collapse of bubbles are utilized for various applications such as cleaning, sonochemistry, and sonoelastography.In addition, the presence of bubbles can modify the speed of sound in the liquid, leading to changes in the wave’s velocity.
This phenomenon, known as acoustic dispersion, is associated with the interaction between the waves and the compressibility of the liquid-gas mixture. Understanding the propagation of ultrasonic waves through liquids containing encapsulated bubbles has practical implications in various fields. In medicine, it is crucial for accurate diagnosis and monitoring of conditions through techniques like ultrasound imaging.
In industrial applications, such as quality control and process monitoring, the behavior of bubbles can provide valuable insights into the properties of liquids and the presence of impurities. Further research is needed to explore the complex dynamics of ultrasonic wave-bubble interactions and their applications. Advances in technology and modeling techniques can contribute to a better understanding of these phenomena and their optimization for specific purposes.
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