The UW team proposes a gentler, more targeted way to guide the stones toward the exit route.
The prototype is a commercial ultrasound system modified to emit pulses only slightly stronger than those used for pregnancy imaging. These sustained, low-intensity waves are just enough to push the crystal through the surrounding fluid.
In the lab, Barbrina Dunmire, an engineer at the Applied Physics Laboratory who helped build the device, points an ultrasound probe at a stone inside a latex kidney. She activates the ultrasonic pulse and the stone immediately swings away through the clear liquid. A doctor would put the probe on a patient's lower back, then use an onscreen ultrasound image to locate the stone and direct the ultrasonic pulse.
Urologists and urology residents at UW Medicine tested three successive prototypes on artificial kidneys and pigs, and helped to design the touchscreen user interface.
"We've had extensive testing in an animal model," said Dr. Jonathan Harper, an assistant professor of urology at UW Medicine. "If it acts in the same way in a human kidney, I think it's extremely promising."
The current Seattle trial is the first time the system is being tested on humans.
Besides guiding kidney stones to help them pass naturally, other applications could be to reposition a stone before or during surgery; to displace a large stone obstructing the ureter to relieve the patient's pain and avoid emergency surgery; and perhaps someday to escort small stones right down the ureter.
If clinical trials go well, researchers believe the device could be used in an urologist's office or by trained emergency room staff, potentially saving hund
|Contact: Hannah Hickey|
University of Washington