Ultrasound Cancer Treatment: Sound Waves Fight Tumors

Summary

For many years, doctors and technicians who performed medical ultrasound procedures viewed bubbles with wary concern. The phenomenon of cavitation—the formation and collapse of tiny gas bubbles due to changes in pressure—was considered an undesirable and largely uncontrollable side effect. But in 2001, researchers at the University of Michigan began exploring ways to harness the phenomenon for the destruction of cancerous tumors and other problematic tissue.The trouble was, creating and controlling cavitation generated heat, which harmed healthy tissue beyond the target area. Zhen Xu, who was working on a Ph.D. in biomedical engineering at the time, was bombarding pig heart tissue in a tank of water with ultrasound when she made a breakthrough.The key was using extremely powerful ultrasound to produce negative pressure of more than 20 megapascals, delivered in short bursts measured in microseconds—but separated by relatively long gaps, between a millisecond and a full second long. These parameters created bubbles that quickly formed and collapsed, tearing apart nearby cells and turning the tissue into a kind of slurry, while avoiding heat buildup. The result was a form of incisionless surgery, a way to wipe out tumors without scalpels, radiation, or heat.“The experiments worked,” says Xu, now a professor at Michigan, “but I also destroyed the ultrasound equipment that I used,” which was the most powerful available at the time. In 2009, she cofounded a company, HistoSonics, to commercialize more powerful ultrasound machines, test treatment of a variety of diseases, and make the procedure, called histotripsy, widely available.So far, the killer app is fighting cancer. In 2023, HistoSonics’ Edison system received FDA approval for treatment of liver tumors. In 2026, clinicians will conclude a pivotal kidney cancer study and apply for regulatory approval. They’ll also launch a large-scale pivotal trial for pancreatic cancer, considered one of the deadliest forms of the d...