Ultrasound technology is being developed to do more than merely allow glimpses into the womb. Doctors are increasingly using sound waves to break up kidney stones and shrink prostate cancer tumors, among other uses.
Now, University of Michigan engineers have developed a new ultrasound approach that can focus high-pressure sound waves so finely that it could lead to an invisible scalpel to perform noninvasive surgery in the near future.
It may sound more like science fiction than medical science, but the device — a carbon-nanotube-coated lens — can focus sound waves tightly enough to generate heat, said Jay Guo, a UM engineering professor who detailed the new technique published in the current issue of the Nature journal Scientific Reports.
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"We believe this could be used as an invisible knife for noninvasive surgery," Guo said. "Nothing pokes into your body, just the ultrasound beam. And it is so tightly focused, you can disrupt individual cells."
Although the device has yet to be tested in human patients, Guo said it might one day give surgeons the ability to operate painlessly because the sound beam is so finely focused it could avoid nerve fibers.
To achieve this superfine beam, the device converts light from a pulsed laser to high-amplitude sound waves through a specially designed lens. The resulting sound waves are 10,000 times higher frequency than humans can hear and create “shockwaves and microbubbles” that could target tiny cancerous tumors, artery-clogging plaques, single cells to deliver drugs, or have applications in cosmetic surgery.
In experiments, the researchers were able to use the device to destroy a single ovarian cancer cell and blast a hole in a kidney stone in less than a minute.
"This is just the beginning," Guo said. "This work opens a way to probe cells or tissues in much smaller scale."
The research was funded by the National Science Foundation and the National Institutes of Health.