Zhen Xu, PhD
One day in the lab in 2002, Dr. Xu was working with various ultrasound parameters in an attempt to damage excised tissue in a water tank. According to Dr. Xu, she was becoming frustrated when her lab mate complained that the parameters she was trying were making a lot of noise. Dr. Xu had been using a pulse repletion frequency within the hearing range, a typical therapeutic ultrasound parameter set.
Unlike diagnostic ultrasound, which is noiseless, the pauses between sound waves created audible noise. Dr. Xu then thought about trying to use microsecond ultrasound pulses and a relatively high pulse repetition frequency to reduce the noise and generate cavitation. Cavitation creates “gas bubbles” in the microseconds between sound waves. The mechanical force generated by the expansion and collapse of these microbubbles can damage things such as kidney stones and metals.
“Cavitation was a physical phenomenon that was known for decades, but everyone’s consensus at the time was that it cannot be controlled enough for soft tissue damage, so people were trying to avoid it in ultrasound imaging or therapy,” said Dr. Xu.
But Dr. Xu decided to turn up the ultrasound pressure as high as it would go—she worried she might even break the device—and intentionally shortened the ultrasound pulses to microsecond- length. According to Dr. Xu, the area of cardiac tissue where she focused the ultrasound point was almost beginning to smoke as tiny tissue debris was destroyed by the focused ultrasound.
HistoSonics’ Edison™ Platform for histotripsy therapy is currently in development and not yet commercially available. Final performance specifications and claims are subject to change pending the completion of regulatory market-access activities.
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