Midwest Moxie: Using sound waves to evaporate tumors - Histosonics

Zhen Xu says the idea behind what became her company Histosonics, started when she arrived at the University of Michigan in 2001 as a first-year PhD student in biomedical engineering, after finishing her bachelor’s degree in China. She recalls being inspired by a pediatric cardiologist who described how surgeons had to create perforations in the hearts of critically ill babies with congenital heart disease - babies who were sometimes dying during surgery - and challenged the lab to invent a non-invasive way to “mechanically remove tissue.” Xu told her mentor, Charles King, that it sounded “wonderfully impossible” and chose it as her dissertation problem. 

Xu says King gave her two unusual pieces of advice: don’t let coursework consume her (he joked her GPA shouldn’t “exceed a minor”), and - more shocking - don’t read research papers at the start, so that conventional thinking wouldn’t constrain an “impossible” project. 

She explains the process of histotripsy - what HistoSonics does - in three parts: (1) focus ultrasound precisely into a small target (about 1–2 mm) using a spherical-surface transducer, (2) use negative pressure to rapidly grow microscopic bubbles from tiny gas pockets already present in the body, and (3) let those bubbles expand and collapse to mechanically pull cells apart, liquefying a tumor into acellular debris that the body clears.

Early work was decidedly unglamorous: she sourced pig hearts by calling a slaughterhouse from the Yellow Pages and, for $5, collecting organs in a trash bag - bare-handed - then experimenting for years. She describes a breakthrough in 2002 after a year of failed tests: to avoid audible pulsing, she increased pulse frequency beyond human hearing and used very short, high-power pulses. In a water tank, she saw a smoke-like plume of tissue debris and a millimeter-sized hole formed through pig heart tissue; after repeating it three times, she ran to King’s office to show him. 

HistoSonics’ Edison system received FDA clearance in 2023 to treat liver tumors and more than 65 hospitals are using it. Xu describes a typical treatment as about an hour including prep, with patients going home the same day and returning to normal activity the next day; she shares an anecdote about a runner completing 20 miles within a week of treatment. Trials are underway for kidney and pancreas tumors and exploration in breast, prostate, thyroid, and even brain tumors “through the skull”. 

A consortium including Jeff Bezos and Peter Thiel acquired a majority stake in HistoSonics in August 2025 for $2.25B, in the second-largest VC-backed medical device transaction ever excluding IPOs or public company acquisitions.