Listening for bubbles to make scuba diving safer

Joshua Currens – jcurrens@unc.edu

Department of Radiology; Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States

Popular version of 5aBAb8 – Towards real-time decompression sickness mitigation using wearable capacitive micromachined ultrasonic transducer arrays
Presented at the 186th ASA Meeting
Read the abstract at https://eppro02.ativ.me/web/index.php?page=Session&project=ASASPRING24&id=482447

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Scuba diving is a fun recreational activity but carries the risk of decompression sickness (DCS), commonly known as ‘the bends’. This condition occurs when divers ascend too quickly, causing gas that has accumulated in their bodies to expand rapidly into larger bubbles—similar to the fizz when a soda can is opened.

To prevent this, divers will follow specific safety protocols that limit how fast they rise to the surface and stop at predetermined depths to allow bubbles in their body to dissipate. However, these are general guidelines that do not account for every person in every situation. This limitation can make it harder to prevent DCS effectively in all individuals without unnecessarily lengthening the time to ascend for a large portion of divers. Traditionally, these bubbles have only been detected with ultrasound technology after the diver has surfaced, so it is a challenge to predict DCS before it occurs (Figure 1b&c). Early identification of these bubbles could allow for the development of personalized underwater instructions to bring divers back to the surface and minimize the risk of DCS.

To address this challenge, our team is creating a wearable ultrasound device that divers can use underwater.

Ultrasound works by sending sound waves into the body and then receiving the echoes that bounce back. Bubbles reflect these sound waves strongly, making them visible in ultrasound images (Figure 1d). Unlike traditional ultrasound systems that are too large and not suited for underwater use, our innovative device will be compact and efficient, designed specifically for real-time bubble monitoring while diving.

Currently, our research involves testing this technology and optimizing imaging parameters in controlled environments like hyperbaric chambers. These are specialized rooms where underwater conditions can be replicated by increasing the inside pressure. We recently collected the first ultrasound scans of human divers during a hyperbaric chamber dive with a research ultrasound system, and next we plan to use it with our first prototype. With this data, we hope to find changes in the images that indicate where bubbles are forming. In the future, we plan to start testing our custom ultrasound tool on divers, which will be a big step towards continuously monitoring divers underwater, and eventually personalized DCS prevention.

divingFigure 1. (a) Scuba diver underwater. (b) Post-dive monitoring for bubbles using ultrasound. (c) Typical ultrasound system (developed using Biorender). (d) Bubbles detected in ultrasound images as bright spots in heart. Images courtesy of JC, unless otherwise noted.

Popping Droplets for Drug Delivery

Aaqib Khan – aaqib.khan@iitgn.ac.in

Chemical Engineering Department, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India

Sameer V. Dalvi – sameervd@iitgn.ac.in
Chemical Engineering Department,
Indian Institute of Technology Gandhinagar
Gandhinagar, Gujarat 382355
India

Popular version of 4pBAa3 – Ultrasound Responsive Multi-Layered Emulsions for Drug Delivery
Presented at the 186th ASA Meeting
Read the abstract at https://eppro02.ativ.me/web/page.php?page=session&project=ASASPRING24&id=3675162

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

What are popping droplets? Imagine you are making popcorn in a pot. Each little popcorn seed consists of a tiny bit of water. When you heat the seeds, the water inside them gets hot and turns into steam. This makes the seed pop and turn into a popcorn. Similarly, think of each popcorn seed as a droplet. The special liquid used to create popping droplets is called perfluoropentane (PFP), which is similar to the water inside the corn seed. PFP can boil at low temperatures and turn into a bubble, which makes it perfect for crafting these special droplets.

Vaporizable/Popping droplets hold great promise in the fields of both diagnosis and therapy. By using sound waves to vaporize PFP present in the droplets, medicine (drugs) can be delivered efficiently to specific areas in the body, such as tumors, while minimizing impacts on healthy tissues. This targeted approach has the potential to improve the safety and effectiveness of therapy, ultimately benefiting patients.

Figure 1. Vaporizable/popping droplets with perfluoropentane (PFP) in the core with successive layers of water and oil

What do we propose? Researchers have been exploring complex structures like double emulsions to load drugs onto droplets (just like filling a backpack with books), especially those that are water-soluble. Building on this, our study introduces multi-layered droplets featuring a vaporizable core (Fig.1). This design enables the incorporation of both water-soluble and insoluble drugs into separate layers within the same droplet. To better visualize this, imagine a club sandwich with layers of bread stacked on top of each other, each layer containing a different filling. Alternatively, picture an onion with multiple stacked layers that can be peeled off one by one. Similarly, multi-layered droplets comprise stacked layers, each capable of holding various substances, such as drugs or therapeutic agents.

To explore the features of the multi-layered droplets further, we carried out two separate studies. First, we estimated the peak negative pressure of the sound wave at which the PFP in the droplets vaporize. This is similar to how water boils at 100°C (212°F) under standard atmospheric pressure, but at low/negative pressure (like under a vacuum), water can boil at low temperatures. Sound waves are known to induce both positive and negative pressure changes. During instances of negative pressure, the pressure drops below the atmospheric pressure, creating a vacuum-like effect. This decrease in pressure can trigger the vaporization of the perfluoropentane (PFP) in the droplets at room temperatures.

Secondly, we loaded a water-insoluble drug, curcumin, which is an anti-inflammatory drug, in the oil layer and estimated the amount of drug loading (just like counting number of books in the backpack).

Figure 2. Relationship between Mean Grayscale (mean brightness) and soundwave pressure for droplet vaporization

Figure 2 depicts the relationship between the increase in mean grayscale (just like the increase in bright areas or brightness of a black-and-white picture) and the peak negative pressure of the sound wave. Based on our study, the peak negative pressure at which the PFP in the droplets was found to vaporize was 6.7 MPa. Furthermore, the loading for curcumin was estimated to be 0.87 ± 0.1 milligrams (mg), which indicates a higher drug loading capacity in multi-layered droplets.

These studies are essential because they help us determine two critical things. The first one allows us to figure out the exact sound wave pressure needed to make the droplets pop. This is useful for the controlled release of drugs in targeted areas. The second study tells us how much drug these droplets can hold, which is helpful in designing drug delivery systems.

Together, these studies enhance our understanding of multi-layered droplets and pave the way for a new targeted therapy, where popping droplets serve as vehicles for delivering drugs or therapeutic agents to specific locations upon activation by sound waves.

A general method to obtain clearer images at a higher resolution than theoretical limit

Jian-yu Lu – jian-yu.lu@ieee.org
X (Twitter): @Jianyu_lu
Instagram: @jianyu.lu01
Department of Bioengineering, College of Engineering, The University of Toledo, Toledo, Ohio, 43606, United States

Popular version of 1pBAb4 – Reconstruction methods for super-resolution imaging with PSF modulation
Presented at the 186 ASA Meeting
Read the abstract at https://eppro02.ativ.me/web/index.php?page=IntHtml&project=ASASPRING24&id=3675355

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Imaging is an important fundamental tool to advance science, engineering, and medicine, and is indispensable in our daily life. Here we have a few examples: Acoustical and optical microscopes have helped to advance biology. Ultrasound imaging, X-ray radiography, X-ray computerized tomography (X-ray CT), magnetic resonance imaging (MRI), gamma camera, single-photon emission computerized tomography (SPECT), and positron emission tomography (PET) have been routinely used for medical diagnoses. Electron and scanning tunneling microscopes have revealed structures in nanometer or atomic scale, where one nanometer is one billionth of a meter. And photography, including the cameras in cell phones, is in our everyday life.

Despite the importance of imaging, it was first recognized by Ernest Abbe in 1873 that there is a fundamental limit known as the diffraction limit for resolution in wave-based imaging systems due to the diffraction of waves. This effects acoustical, optical, and electromagnetic waves, and so on.

Recently (see Lu, IEEE TUFFC, January 2024), the researcher developed a general method to overcome such a long-standing diffraction limit. This method is not only applicable to wave-based imaging systems such as ultrasound, optical, electromagnetic, radar, and sonar; it is in principle also applicable to other linear shift-invariant (LSI) imaging systems such as X-ray radiography, X-ray CT, MRI, gamma camera, SPECT, and PET since it increases image resolution by introducing high spatial frequencies through modulating the point-spread function (PSF) of an LSI imaging system. The modulation can be induced remotely from outside of an object to be imaged, or can be small particles introduced into or on the surface of the object and manipulated remotely. The LSI system can be understood with a geometric distortion corrected optical camera in the photography, where the photo of a person will be the same or invariant in terms of the size and shape if the person only shifts his/her position in the direction that is perpendicular to the camera optical axis within the camera field of view.

Figure 1 below demonstrates the efficacy of the method using an acoustical wave. The method was used to image a passive object (in the first row) through a pulse-echo imaging or to image wave source distributions (in the second row) with a receiver. The best images obtainable under the Abbe’s diffraction limit are in the second column, and the super-resolution (better than the diffraction limit) images obtained with the new method are in the last column. The super-resolution images had a resolution that was close to 1/3 of the wavelength used from a distance with an f-number (focal distance divided by the diameter of the transducer) close to 2.

Figure 1. This figure was modified in courtesy of IEEE (doi.org/10.1109/TUFFC.2023.3335883).

Because the method developed is based on the convolution theory of an LSI system and many practical imaging systems are LSI, the method opens an avenue for various new applications in science, engineering, and medicine. With a proper choice of a modulator and imaging system, nanoscale imaging with resolution similar to that of a scanning electron microscope (SEM) is possible even with visible or infrared light.

Wearable Ultrasound Monitor Can Aid Rehabilitation from Injury #Acoustics23

Wearable Ultrasound Monitor Can Aid Rehabilitation from Injury #Acoustics23

A new approach to ultrasound imaging can provide real-time insights into muscle dynamics.

SYDNEY, Dec. 5, 2023 – Millions suffer from musculoskeletal injuries every year, and the recovery process can often be long and difficult. Patients typically undergo rehabilitation, slowly rebuilding muscle strength as their injuries heal. Medical professionals routinely evaluate a patient’s progress via a series of tasks and exercises. However, because of the dynamic nature of these exercises, obtaining a clear picture of real-time muscle function is extremely challenging.

Parag Chitnis of George Mason University led a team that developed a wearable ultrasound system that can produce clinically relevant information about muscle function during dynamic physical activity. He will present his work Dec. 5 at 5:00 p.m. Australian Eastern Daylight Time, as part of Acoustics 2023 running Dec. 4-8 at the International Convention Centre Sydney

Wearable Ultrasound

A wearable ultrasound monitor can provide insight into dynamic muscle movement during activities like jumping. Credit: Parag Chitnis

Many medical technologies can give doctors a window into the inner workings of a patient’s body, but few can be used while that patient is moving. A wearable ultrasound monitor can move with the patient and provide an unprecedented level of insight into body dynamics.

“For instance, when an individual is performing a specific exercise for rehabilitation, our devices can be used to ensure that the target muscle is actually being activated and used correctly,” said Chitnis. “Other applications include providing athletes with insights into their physical fitness and performance, assessing and guiding recovery of motor function in stroke patients, and assessing balance and stability in elderly populations during routine everyday tasks.”

Designing a wearable ultrasound device took much more than simply strapping an existing ultrasound monitor to a patient. Chitnis and his team reinvented ultrasound technology nearly from scratch to produce the results they needed.

“We had to completely change the paradigm of ultrasound imaging,” said Chitnis. “Traditionally, ultrasound systems transmit short-duration pulses, and the echo signals are used to make clinically usefully images. Our systems use a patented approach that relies on transmission of long-duration chirps, which allows us to perform ultrasound sensing using the same components one might find in their car radio.”

This modified approach allowed the team to design a simpler, cheaper system that could be miniaturized and powered by batteries. This let them design an ultrasound monitor with a small, portable form factor that could be attached to a patient.

Soon, Chitnis hopes to further improve his device and develop software tools to more quickly interpret and analyze the ultrasound signals.

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Contact:
AIP Media
301-209-3090
media@aip.org

———————– MORE MEETING INFORMATION ———————–

The Acoustical Society of America is joining the Australian Acoustical Society to co-host Acoustics 2023 Sydney. This collaborative event will incorporate the Western Pacific Acoustics Conference and the Pacific Rim Underwater Acoustics Conference.

Main meeting website: https://acoustics23sydney.org/
Technical program: https://eppro01.ativ.me/src/EventPilot/php/express/web/planner.php?id=ASAFALL23

ASA PRESS ROOM
In the coming weeks, ASA’s Press Room will be updated with newsworthy stories and the press conference schedule at https://acoustics.org/asa-press-room/.

LAY LANGUAGE PAPERS
ASA will also share dozens of lay language papers about topics covered at the conference. Lay language papers are summaries (300-500 words) of presentations written by scientists for a general audience. They will be accompanied by photos, audio, and video. Learn more at
https://acoustics.org/lay-language-papers/.

PRESS REGISTRATION
ASA will grant free registration to credentialed and professional freelance journalists. If you are a reporter and would like to attend the meeting or virtual press conferences, contact AIP Media Services at media@aip.org. For urgent requests, AIP staff can also help with setting up interviews and obtaining images, sound clips, or background information.

ABOUT THE ACOUSTICAL SOCIETY OF AMERICA
The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See https://acousticalsociety.org/.

ABOUT THE AUSTRALIAN ACOUSTICAL SOCIETY
The Australian Acoustical Society (AAS) is the peak technical society for individuals working in acoustics in Australia. The AAS aims to promote and advance the science and practice of acoustics in all its branches to the wider community and provide support to acousticians. Its diverse membership is made up from academia, consultancies, industry, equipment manufacturers and retailers, and all levels of Government. The Society supports research and provides regular forums for those who practice or study acoustics across a wide range of fields The principal activities of the Society are technical meetings held by each State Division, annual conferences which are held by the State Divisions and the ASNZ in rotation, and publication of the journal Acoustics Australia. https://www.acoustics.org.au/

Needle-Free Ultrasound Vaccine Delivery #Acoustics23

Needle-Free Ultrasound Vaccine Delivery #Acoustics23

Technique employs bubbles formed and popped in response to sound waves to deliver vaccines and achieve potentially improved immune response.

SYDNEY, Dec. 4, 2023 – An estimated quarter of adults and two-thirds of children have strong fears around needles, according to the U.S. Centers for Disease Control and Prevention. Yet, public health depends on people being willing to receive vaccines, which are often administered by a jab.

Darcy Dunn-Lawless, a doctoral student at the University of Oxford’s Institute of Biomedical Engineering, is investigating the potential of a painless, needle-free vaccine delivery by ultrasound. He will share the recent advancements in this promising technique as part of Acoustics 2023 Sydney, running Dec. 4-8 at the International Convention Centre Sydney. His presentation will take place Dec. 4 at 11:00 a.m. Australian Eastern Daylight Time.

“Our method relies on an acoustic effect called ‘cavitation,’ which is the formation and popping of bubbles in response to a sound wave,” said Dunn-Lawless. “We aim to harness the concentrated bursts of mechanical energy produced by these bubble collapses in three main ways. First, to clear passages through the outer layer of dead skin cells and allow vaccine molecules to pass through. Second, to act as a pump that drives the drug molecules into these passages. Lastly, to open up the membranes surrounding the cells themselves, since some types of vaccine must get inside a cell to function.”

Though initial in vivo tests reported 700 times fewer vaccine molecules were delivered by the cavitation approach compared to conventional injection, the cavitation approach produced a higher immune response. The researchers theorize this could be due to the immune-rich skin the ultrasonic delivery targets in contrast to the muscles that receive the jab. The result is a more efficient vaccine that could help reduce costs and increase efficacy with little risk of side effects.

“In my opinion, the main potential side effect is universal to all physical techniques in medicine: If you apply too much energy to the body, you can damage tissue,” Dunn-Lawless said. “Exposure to excessive cavitation can cause mechanical damage to cells and structures. However, there is good evidence that such damage can be avoided by limiting exposure, so a key part of my research is to try and fully identify where this safety threshold lies for vaccine delivery.”

Vaccine

Ultrasound pulses deliver vaccines through the skin without needles. This technique, which employs sound waves to create bubbles that forge a path for the vaccine, may be especially helpful for DNA vaccines. Credit: Darcy Dunn-Lawless

Dunn-Lawless works as part of a larger team under the supervision of Dr. Mike Gray, Professor Bob Carlisle, and Professor Constantin Coussios within Oxford’s Biomedical Ultrasonics, Biotherapy and Biopharmaceuticals Laboratory (BUBBL). Their cavitation approach may be particularly conducing to DNA vaccines that are currently difficult to deliver. With cavitation able to help crack open the membranes blocking therapeutic access to the cell nucleus, the other advantages of DNA vaccines, like a focused immune response, low infection risk, and shelf stability, can be better utilized.

###

Contact:
AIP Media
301-209-3090
media@aip.org

———————– MORE MEETING INFORMATION ———————–

The Acoustical Society of America is joining the Australian Acoustical Society to co-host Acoustics 2023 Sydney. This collaborative event will incorporate the Western Pacific Acoustics Conference and the Pacific Rim Underwater Acoustics Conference.

Main meeting website: https://acoustics23sydney.org/
Technical program: https://eppro01.ativ.me/src/EventPilot/php/express/web/planner.php?id=ASAFALL23

ASA PRESS ROOM
In the coming weeks, ASA’s Press Room will be updated with newsworthy stories and the press conference schedule at https://acoustics.org/asa-press-room/.

LAY LANGUAGE PAPERS
ASA will also share dozens of lay language papers about topics covered at the conference. Lay language papers are summaries (300-500 words) of presentations written by scientists for a general audience. They will be accompanied by photos, audio, and video. Learn more at
https://acoustics.org/lay-language-papers/.

PRESS REGISTRATION
ASA will grant free registration to credentialed and professional freelance journalists. If you are a reporter and would like to attend the meeting or virtual press conferences, contact AIP Media Services at media@aip.org. For urgent requests, AIP staff can also help with setting up interviews and obtaining images, sound clips, or background information.

ABOUT THE ACOUSTICAL SOCIETY OF AMERICA
The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See https://acousticalsociety.org/.

ABOUT THE AUSTRALIAN ACOUSTICAL SOCIETY
The Australian Acoustical Society (AAS) is the peak technical society for individuals working in acoustics in Australia. The AAS aims to promote and advance the science and practice of acoustics in all its branches to the wider community and provide support to acousticians. Its diverse membership is made up from academia, consultancies, industry, equipment manufacturers and retailers, and all levels of Government. The Society supports research and provides regular forums for those who practice or study acoustics across a wide range of fields The principal activities of the Society are technical meetings held by each State Division, annual conferences which are held by the State Divisions and the ASNZ in rotation, and publication of the journal Acoustics Australia. https://www.acoustics.org.au/