New "Ultrasound on a Chip" Tool Could Revolutionize Medical Imaging

A smartphone screen displays an ultrasound image. Attached to the smartphone is a black ultrasound wand.
Photo: Butterfly Network

Jonathan Rothberg, a entrepreneur who prides himself on drastically disrupting the biomedical industry every so often, has typically big claims for his new product. The Butterfly iQ, a cheap handheld ultrasound tool with AI smarts tucked inside, will 1) revolutionize medical imaging in hospitals and clinics, 2) change the game in global health, and 3) eventually become a consumer product that will be as ubiquitous as the household thermometer, he says. 

Today, Rothberg’s startup Butterfly Network unveiled the tool and announced its FDA clearance for 13 clinical applications, including cardiac scans, fetal and obstetric exams, and musculoskeletal checks. Rather than using a dedicated piece of hardware for the controls and image display, the iQ works with the user’s iPhone. The company says it will start shipping units in 2018 at an initial price of about $2,000.

Photo shows a medical professional holding a smartphone in one hand and an ultrasound wand in the other hand
Photo: Butterfly Network

But that’s just the beginning, Rothberg tells IEEE Spectrum. He expects to bring the price down on the handheld gadget, and is already looking ahead to radically new products. “In the next two years we’ll release a patch that uses ultrasound to monitor patients, and a pill you can swallow to look at cancer from within the body,” he says.

All these form factors are possible because Butterfly uses a very different technology than conventional ultrasound. Its “ultrasound on a chip” takes advantage of the mass-market fabrication techniques perfected for computer chips, Rothberg says. “We put all the elements onto a semiconductor wafer, then we can dice up the wafer to make 48 ultra low-cost ultrasound machines,” he says.

Today’s ultrasound systems use piezoelectric crystals, which convert electrical energy into vibrations in the form of ultrasonic waves. A typical system has a display screen on a bulky cart with several wands for imaging at different depths within the body. These machines can cost upwards of $100,000. While a few smaller and cheaper devices exist, such as GE’s handheld Vscan products, they still use pricey piezoelectric technology and require multiple probes, bringing the price to something between $8,000 and $20,000.

Developing the iQ’s chip-based technology was a two-step process. First, Butterfly’s engineers replaced the piezoelectrics with a micromachine that acts like a tiny drum to generate vibrations. Inside this “capacitive micromachined ultrasound transducer” (CMUT), an applied voltage moves a membrane to send ultrasonic waves into the body. The waves that bounce back from various body tissues move the membrane and are registered as an electric signal, which creates the image. Butterfly based its technology on research done by Stanford professor Pierre Khuri-Yakub, who serves on Butterfly’s scientific advisory board.

Photo shows a semiconductor chip held between finger and thumb.
Photo: Butterfly Network

Rothberg explains that typical ultrasound systems require separate probes for different clinical applications because the crystals have to be tuned at the time of manufacture to produce the right type of ultrasonic wave for imaging at a particular depth. But the Butterfly iQ can be tuned on the fly. “We have 10,000 of these micromachine transducers on a probe, and that gives us a monster dynamic range,” he says. "We can make them buzz at 1 megahertz if we want to go deep, or 5 megahertz if we want to go shallow.”

The second innovation was to do away with the wiring that connects a typical piezoelectric probe to the electronic controls and displays. Butterfly’s micromachines are attached directly to a semiconductor layer that contains all the necessary amplifiers, signal processors, and so on.

Independent experts say the technology sounds promising, but they’ll wait to see if the Butterfly iQ can live up to Rothberg’s claims. “People in medicine tend to be conservative, and I’m skeptical when someone claims to have found a wonderdrug or cure,” says Torben Becker, an emergency room physician at the University of Florida hospital who has researched the use of portable ultrasound tools by paramedics and in the developing world

Becker says portable ultrasound tools are currently a niche technology—some ER doctors are experimenting with them, he says, but they haven’t caught on. “There’s definitely an argument to be made for having something that you can pull out of your pocket and use in an exam,” he says. But the portable tools he has tried thus far had inferior image quality to the big systems, Becker says. He also ran into difficulties with transmitting the images to the hospital’s database for storage. “And saving those images is required to bill for the scan,” he notes.

Beyond price and portability, the Butterfly iQ’s other big selling point is its incorporation of artificial intelligence for both image acquisition and analysis. The Butterfly engineers trained the software on vast datasets of ultrasound images, teaching it the difference between a high- and poor-quality image for body parts like the heart. When the user brings the probe to a patient’s chest for a cardiac exam, the iPhone display helps them find the right spot. It also does some simple analysis of the resulting ultrasound image, such as measuring the “ejection fraction” that indicates how well a heart is pumping out blood.  

At Butterfly Network’s New York City office, two members of the machine learning team kindly gave IEEE Spectrum a demonstration of the technology at work:

The AI component is what makes the iQ a potential game-changer for both health care in the developing world and for well-off consumers. In the global health context, Butterfly Network envisions the tool being used at rural health clinics where the staff doesn’t have expertise with ultrasound; with the iQ’s guidance system, they could nevertheless acquire a proper image and either send it to an expert or use the system’s guidance to figure out the next step. 

In the United States and other prosperous parts of the world, the tool could empower consumers, relieve anxiety, and reduce health care costs by eliminating many doctor visits, says John Martin, Butterfly Network’s chief medical officer. “I absolutely think the ultrasound device will be in everybody’s house,” Martin says. For example, if a child falls and complains of a pain in the arm, the parents could do a quick ultrasound to check the bone, maybe sending that image to their pediatrician rather than making tracks to the ER.   

The FDA hasn’t yet approved the tool for at-home use, but Martin says the path to that approval is well established. “When the first thermometers were made, when the first blood pressure cuffs were made, they were only in hospitals,” he says. “Think about defibrillators, which used to only be in hospitals but are now in every mall and office—someone off the street can now deliver an electric shock to someone’s heart.” If Butterfly Network has its way, a stranger off the street could one day easily take a gander at your innards. 

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