THE FUTURE OF PORTABLE ULTRASOUND- IS WEARABLE!

By: Lennard M. Goetze, Ed.D

An ever-expanding portion of the medical community recognize ultrasound advancements for its non-invasive, real-time and non-radiation safety. Since the advent of medical ultrasound for fetal imaging (in 1956), developers have propelled the global movement to advance its capacity to scan deeper & wider, to go portable and to record more biometric data.

Scientists and clinicians alike have advanced ultrasound applications to benefit a wide variety of medical applications.  This includes its abilities to study: MSK/musculoskeletal injuries, breast health (screening), abnormal tissues and cancerous masses, cardiac performance (echocardiography), kidney disorders/renal blood flow monitoring and ophthalmic scanning of ocular structures. 

Amidst the Covid-19 Pandemic, an astounding report from MIT NEWS (7/28/2022) reported on engineers who developed a 2x3cm postage-stamp sized wearable ultrasound Patch that can "see inside the body".  This innovation offered continuous imaging of internal organs for 48 hours or longer (contingent upon the life of the rechargeable power supply).

Clinicians and researchers are impressed by the range of possibilities for the use of this innovation as the news continues to spread throughout the radiological community about this next clinical scanning "game-changer".  "I learned about Dr. Zhao's work at the thick of the pandemic and the very idea of a wearable scanner clearly raises the bar in the current trend in portable ultrasound designs", says Dr. Robert L. Bard, cancer imaging radiologist and principal investigator of IHRC (Integrative Health Research Center) in NYC. "Since Covid (19), ambulance rigs, triage units and ER's took full advantage of the many hand-held ultrasounds in the market... they called it the digital stethoscope. Where conventional ultrasound allows us to detect and diagnose pathology on the examination table or during a procedure, the idea of a patient wearing the ultrasound for 48 hours marks a new era in data collecting or biometric research."

THE ULTRASOUND PATCH TECHNOLOGY (Excerpt from MIT news)

MIT engineers have developed a small ultrasound sticker that can monitor the stiffness of organs deep inside the body. The sticker, about the size of a postage stamp, can be worn on the skin and is designed to pick up on signs of disease, such as liver and kidney failure and the progression of solid tumors. [1][2]

The probe is attached to a flexible circuit, which activates the ultrasound transducers, collects the ultrasound echoes, amplifies and filters these echoes, and transmits the digitized signal to a terminal device. The entire system is powered by a commercial rechargeable lithium polymer battery.[3]

In an exclusive (3/8/2024) special interview with development team leader and senior author Dr. Xuanhe Zhao -mechanical & environmental engineer at MIT, the imaging system he aptly calls "the ultrasound patch", HealthTech Reporter presents this imaging innovation to “advance noninvasive scanning into the body’s workings in real time, providing clinicians with live & recorded images of a patient’s internal organs for up to 24 hours”. 

EXCUSLIVE INTERVIEW WITH DR. ZUANHE ZHAO

The origins of this design started with a student Chonghe Wang- who got his Masters Degree from Harvard University. He joined my research and development group on a graduate level, focusing on ultrasound imaging. We worked together on this dream about a wired ultrasound device that's wearable on the body.  Wang made the ultrasound probe to be soft and stretchable- so you can put on different locations on the body. Then the challenge is creating quality ultrasound imaging. Imagine the camera in your cell phone- if you stretch the camera sensor, you distort the image dramatically, degrading the image quality.

Together with my team, we came up with a fundamentally new idea- to shrink the handheld ultrasound probe to a thin, but a very rigid ultrasound probe. As probes are rigid, you cannot stretch it. We also had to figure out how to conform this rigid probe to different locations of the body. We needed to invent a bio-adhesive coupling- a gooey,  jello-like adhesive to attach to different locations and skin surfaces of the body while (at the same time) adhering the ultrasound to the body for lengthy periods of time. Immediately, we realized (that) now we can have a very high quality ultrasound imaging similar to the handheld ultrasound probes.

We developed this patch to be a long term and continuous use for variable imaging.  Similar to an EKG patch that you adhere a few patches on the body, our ultrasound patch adheres to the corresponding location of the body for long-term continuous imaging. 

The core design allows you to conduct B mode imaging, Doppler mode to measure blood flow and Elasticity mode to measure the elasticity, the rigidity of the tissues in the same ultrasound sticker- at the same time! Since we first published this idea in 2022, we received incredible attention from the (medical) society to keep expanding.  In addition to measuring images of deeper internal organs, continued development now allows us to also scan for blood flow (3D Doppler) and the rigidity of different organs (Elastography) with this ultrasound patch -as another variable. 

Expanding the functions of our ultrasound patch to add elastography is so useful because when organs develop diseases, they usually change their stiffness. For example, tumors are usually stiffer than the surrounding soft tissues. When an organ like the liver is undergoing acute liver failure, it becomes stiffer than the healthy state. By continuously measuring the organ's rigidity, you can do early diagnosis of different types of disease. If this organ under monitoring shows change in rigidity, we can assess that maybe there's something wrong- enough to mitigate. A situation like this will be the potential impact. 

IMAGE 3: Each of the dots is one PIEZOelectric transducer. When you apply voltage on it, it sends a pulse to the body. Then your organ surface will reflect that wave and it will be received by either that or other transducers on this ultrasound probe. Then we translate that electrical signal into (measurable) imaging information or doppler mode data etc. 

In our current version, we have a cable connected to that sticker that's connected to a device called VERASONICS (the size of a desktop computer). So that's not a miniaturized machine that's, uh, the size of, uh, desktop computer. That demonstrate the capability of this device for hospital use. In my group, we already achieved a miniaturized version of device- sized similar to a cell phone or even smaller. You can put it in your pocket, or you can wire somewhere on the body that is a fully integrated.  The battery, the imaging processing, the CPU- everything is in this package. Then this package communicates with your cell phone or with your computer via Bluetooth.  It transmits the imaging data to your device. 

 Source: MITNews Video:

A team of engineers have designed a stamps size device that sticks to the skin and can provide continuous ultrasound imaging of internal organs for 48 hours. The current design requires connecting the stickers to instruments that translate the reflected sound waves into images. However, if the devices can be made to operate wirelessly, a goal the team is currently working toward, the ultrasound stickers could be made into wearable imaging products that patients could take home from a doctor's office or even buy at a pharmacy. The entire ultrasound sticker measures about two square centimeters across and three millimeters thick about the area of a postage stamp. The bottom elastomer layer is designed to stick to the skin while the top layer adheres to a rigid array of transducers. The team also designed and fabricated this pairing of stretchy adhesive layers with a rigid array, enables the device to conform to the skin while remaining in position to generate clear, precise images.

The device's bottom adhesive layer is made from two thin layers of elastomer that encapsulate a middle layer of solid hydrogel. The elastomer layers prevent dehydration of the hydrogel. According to the researchers. Only when hydrogel is highly hydrated can acoustic waves penetrate effectively and give high resolution imaging of internal organs. The researchers ran the ultrasound sticker through a battery of tests with healthy volunteers who wore the stickers on various parts of their bodies. The stickers stayed attached to their skin and produced clear images of underlying structures for up to 48 hours. As the researchers work to make their design completely wireless, they point out that even in their current form, an immediate application could include continuously imaging internal organs of patients in hospitals without requiring a technician to hold a probe in place for long periods of time while continuing to reapply the necessary liquid gel, which acts to transmit ultrasound waves.

CONTINUED PURSUIT OF IMAGING REVOLUTION

We continue to develop many other technologies moving this field forward. In addition to fundamental scientific research, because this technology is so promising, we receive so many requests for upgrades as well as samples for clinical use. 

Our ultrasound patch is currently approved for MIT IRB for imaging healthy human subjects. We are collaborating with Harvard Medical School and Stanford Medical School to image patients in hospitals. Our next step is to undergo FDA approvals for this ultrasound patch technology- however, because this is a noninvasive imaging modality, and because the power induced by the ultrasound sticker is even lower than that of the conventional handheld ultrasound,  we do not expect, too much difficulty or too many surprises in obtaining FDA approval. But we remain careful with GMP (Good Manufacturing Practices) of the whole system to earn FDA approval. 

Our wearable ultrasound sticker technology will potentially impact both the healthcare by providing long-term continuous monitoring of diverse diseases.  It shows promise in impacting the fundamental biological research by providing a new long-term/continuous window to image diverse organs simultaneously. We are very excited about the future of this ultrasound imaging technology. 

References

1) https://news.mit.edu/2022/ultrasound-stickers-0728

2) https://news.mit.edu/2024/ultrasound-sticker-senses-changing-stiffness-deep-internal-organs-0209#:~:text=MIT%20engineers%20have%20developed%20a,the%20progression%20of%20solid%20tumors.

3) https://www.nibib.nih.gov/news-events/newsroom/wireless-wonder-wearable-ultrasound-patch-goes-completely-cable-free#:~:text=The%20probe%20is%20attached%20to,commercial%20rechargeable%20lithium%20polymer%20battery.

*All images are courtesy of MIT News and/or Dr. Xuanhe Zhao

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