In the decades following the deployment of the first clinical ultrasound machine in 1956, high-frequency scanners have become a go-to tool in many clinicians’ diagnostic arsenals — at least in the developed world. Unfortunately, despite the proliferation of smaller, cheaper devices like GE’s Vscan, they remain prohibitively expensive. The going price for a single machine is between $9,000 and $20,000, with individual scans costing about $250.

That’s because traditional ultrasound machines rely on transducers containing quartz crystals and other specialized components to generate images. But Butterfly, a startup cofounded by 2015 National Medal of Technology and Innovation award recipient and Carnegie Mellon graduate Jonathan Rothberg, claims to have pioneered a technologically superior alternative. The company‘s eponymous $2,000 Butterfly iQ shrinks ultrasound tech down to a peripheral the size of an electric razor.

Butterfly today announced that it has raised $250 million in a Series D funding round led by Fidelity, with participation from Fosun Pharma, the Bill & Melinda Gates Foundation, and Jamie Dinan, along with other returning and existing investors.

Butterfly iQ

Above: Butterfly iQ actively imaging a patient’s chest tissue.

Image Credit: Butterfly iQ

“This is an important step in fulfilling the promise of bringing ultrasound to the millions that do not have access to this essential medical technology,” Rothberg said earlier this year. “I set out to democratize ultrasound imaging as I did with DNA sequencing. Two-thirds of the world has no access to medical imaging, and even in the developed world, expense and lack of expertise limit its accessibility.”

Butterfly iQ, which produces “clinical-quality” ultrasounds uploaded via iPhone to Butterfly’s cloud storage service, was cleared by the Federal Food and Drug Administration (FDA) in October 2017 for abdominal, cardiovascular, fetal, gynecological, urological, musculoskeletal, and seven other clinical applications.

Off-the-shelf ultrasound scanners apply an electric current to a crystal (or multiple crystals) to create vibrations and, subsequently, sound waves. (It’s known as the piezoelectric effect.) Those waves travel through the body until they hit a boundary between tissues or organs, after which some reflect back to the crystal and create an electrical current on contact. Because the speed of sound in body tissue remains constant and because the return time of each echo can be easily measured, the scanners’ compute units are able to gauge the distance between the transducer and boundaries. Their calculations factor into the final image.

Butterfly iQ Clinical

Above: A doctor demoing the Butterfly iQ app to a patient.

Image Credit: Butterfly

Butterfly iQ’s ultrasound-on-a-chip — a semiconductor wafer containing discrete signal processors and amplifiers — functions as a conventional transducer but trades crystals for layers of capacitive micromachined ultrasound transducers (CMUTs) — basically, drum-like metal plates suspended between two electrodes. A single chip has as many as 10,000 transducer channels that, when supplied with electricity, resonate at frequencies tailored to different tissue types. Thanks to a unique “butterfly network” architecture that intelligently delegates processing among the channels, iQ can perform roughly half a trillion operations per second in the course of a scan — enough for a three-dimensional ultrasound image of any region of the body.

iQ is the world’s first ultrasound-on-a-chip capable of whole-body imaging, Butterfly says. Traditional transducer crystals have to be tuned to generate ultrasonic waves for particular depths, but its silicon has no such constraints; adjustments to the CMUTs’ electrical field allow it to switch frequencies on the fly. “We can make them buzz at 1 megahertz if we want to go deep, or 5 megahertz if we want to go shallow,” Rothberg said, speaking to IEEE Spectrum.

The hardware’s only half of the equation, of course, but Butterfly’s software ecosystem is equally as robust. The iQ’s companion smartphone app taps artificial intelligence (AI) to streamline the setup process. Computer vision algorithms ingest footage from the handset’s camera and detect the probe’s location in real time, directing users through augmented reality (AR) prompts precisely where to position it. (Butterfly calls it “Tele-Guidance.”) Another AI system performs a quality check on each image and a simple analysis, but that won’t ship in the first wave of production devices — it is waiting on a separate FDA approval.

Butterfly iQ Product

Above: Butterfly iQ’s small enough to fit in a pant pocket.

Image Credit: Butterfly

The cloud storage service to which images are uploaded is AES 256-bit encrypted and SOC II certified, and fully compliant with HIPPA, the 1996 U.S. law designed to protect personal information collected in medical records. Its built-in sharing tools let users comment on images, send messages, and share scans with colleagues in the form of secure links.

Rothberg, who invented the world’s first DNA sequencer chip (the Ion Torrent) and developed a metastatic breast cancer treatment that’s still in use today, said his work in ultrasound was inspired by a presentation from prolific MIT physicist Max Tegmark. Tegmark postulated that a system with thousands of antennas could measure energy more efficiently than any single transducer, which Rothberg, whose oldest daughter suffers from tuberous sclerosis, thought could be applied to ultrasound imaging.

With Tegmark’s blessing and the help of one of his graduate students, Nevada Sanchez, Rothberg and a team of about 50 scientists, developers, and engineers built the tech that makes the iQ tick — the aforementioned butterfly network — on the back of research by Stanford professor Pierre Khuri-Yakub. It took eight years of R&D, but John Martin, Butterfly’s chief medical officer, is adamant that it was well worth the wait. He has reason to be: While testing iQ three years ago, he discovered a tumor under his tongue — a squamous cell that he’d earlier dismissed as an overactive lymph node.

Butterfly iQ Product

Above: Butterfly iQ plugged into a smartphone.

Image Credit: Butterfly

The first units begin shipping today to the tens of thousands of customers who reserved them. Rothberg hopes to partner with nonprofits and universities to bring it to the developing world. To that end, in April Butterfly and a Brown University ultrasound team piloted iQ in the intensive care units in Kenyan hospitals.

The plan is to sell more than a quarter of a million devices in the next 18 months, but Butterfly’s already hard at work on two new products: a patch that uses ultrasound to monitor patients and an ingestible pill that looks at cancer from within the body. Rothberg believes that one day the firm’s platform will replace the stethoscope.