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Improving burst wave lithotripsy effectiveness for small stones and fragments by increasing frequency: theoretical modeling and ex vivo study

Bailey, Michael R. and Maxwell, Adam D. and Cao, Shunxiang and Ramesh, Shivani and Liu, Ziyue and Williams, James Caldwell, Jr. and Thiel, Jeff and Dunmire, Barbrina and Colonius, Tim and Kuznetsova, Ekaterina and Kreider, Wayne and Sorensen, Mathew D. and Lingeman, James E. and Sapozhnikov, Oleg A. (2022) Improving burst wave lithotripsy effectiveness for small stones and fragments by increasing frequency: theoretical modeling and ex vivo study. Journal of Endourology . ISSN 0892-7790. doi:10.1089/end.2021.0714. (In Press)

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Introduction and Objective: In clinical trial NCT03873259, a 2.6-mm lower pole stone was treated transcutaneously and ex vivo with 390-kHz burst wave lithotripsy (BWL) for 40 minutes and failed to break. The stone was subsequently fragmented with 650-kHz BWL after a 4-minute exposure. This study investigated how to fragment small stones and why varying BWL frequency may more effectively fragment stones to dust. Methods: A linear elastic model was used to calculate the stress created inside stones from shock wave lithotripsy (SWL) and different BWL frequencies mimicking the stone’s size, shape, lamellar structure, and composition. To test model predictions about the impact of BWL frequency, matched pairs of stones (1-5 mm) were treated at 1) 390 kHz, 2) 830 kHz, and 3) 390 kHz followed by 830 kHz. The mass of fragments greater than 1 and 2 mm was measured over 10 minutes of exposure. Results: The linear elastic model predicts that the maximum principal stress inside a stone increases to more than 5.5 times the pressure applied by the ultrasound wave as frequency is increased, regardless of composition tested. The threshold frequency for stress amplification is proportionate to the wave speed divided by the stone diameter. Thus, smaller stones may be likely to fragment at higher frequency, but not lower frequency below a limit. Unlike with SWL, this amplification in BWL occurs consistently with spherical and irregularly shaped stones. In water tank experiments, stones smaller than the threshold size broke fastest at high frequency (p=0.0003), whereas larger stones broke equally well to sub-millimeter dust at high, low, or mixed frequency. Conclusions: For small stones and fragments, increasing frequency of BWL may produce amplified stress in the stone causing the stone to break. Using the strategies outlined here, stones of all sizes may be turned to dust efficiently with BWL.

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Colonius, Tim0000-0003-0326-3909
Additional Information:© 2022 Mary Ann Liebert, Inc. Online Ahead of Editing: March 1, 2022.
Record Number:CaltechAUTHORS:20220412-864423600
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Official Citation:Dr. Michael R Bailey, Dr. Adam D Maxwell, Dr. Shunxiang Cao, Miss Shivani Ramesh, Dr. Ziyue Liu, Dr. James Caldwell Williams Jr., Mr. Jeff Thiel, Mrs. Barbrina Dunmire, Prof. Tim Colonius, Ms. Ekaterina Kuznetsova, Dr. Wayne Kreider, Dr. Mathew D. Sorensen, Dr. James E Lingeman, and Prof. Oleg A. Sapozhnikov. Journal of Endourology. ahead of print;
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114236
Deposited By: Tony Diaz
Deposited On:12 Apr 2022 16:17
Last Modified:12 Apr 2022 16:17

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