2015: A new method of lithotripsy using ultrasound to fragment kidney stones is developed


Collaborative research of physicists from Moscow State University and engineers and medical doctors from the University of Washington led to the development of a new method of treatment of urolithiasis using intense ultrasound bursts.

About 10% of the population suffers from kidney stones. The most common treatment for kidney stones is shock wave lithotripsy (SWL). SWL is a noninvasive procedure where shock waves are focused into the body and onto the stone, shattering it into small fragments that the patient will pass spontaneously. Because it is noninvasive, SWL is the treatment most preferred by patients. Unfortunately, this procedure is unsuccessful about 40% of the time, and large residual stone fragments sometimes remain that require repeat treatments or alternative, more invasive methods of extraction. Scientific team at Moscow State University led by Prof. Oleg Sapozhnikov and researchers at the University of Washington — Lawrence Crum, Michael Bailey, Adam Maxwell, Wayne Kreider and others have been performing SWL research for nearly 20 years. Through simulations and experiments, the joint research has led the collaborative team to understand more precisely the physical principles for how shock waves fracture kidney stones. Based on this work, an alternative noninvasive method to fragment stones was recently developed that uses ultrasound pulses rather than shock waves to fragment stones, called burst wave lithotripsy or BWL. Ultrasound bursts consist of consecutive acoustic cycles that can accumulate to concentrate energy within the stone, enabling comminution at relatively low peak pressures of the incident sound field. In this way, BWL can cause stresses and fractures in the stone through resonances. A key characteristic of this method is that the size fragments generated when the stone disintegrates is controlled by the ultrasound frequency. In this way, the technique can be 'tuned' to create small fragments that the patients will pass naturally, and potentially improve the success rate of lithotripsy procedures.

The results of this work have been published in the paper: Maxwell A.D., Cunitz B.W., Kreider W., Sapozhnikov O.A., Hsi R.S., Harper J.D., Bailey M.R., and SorensenM.D. “Fragmentation of renal calculi in vitro by focused ultrasound bursts”, J. Urology,193(1),338-344 (2015).