The University of Washington team deserves to be congratulated for developing burst wave lithotripsy (BWL) technology within 5 years from concept, through in vitro1 and in vivo2 studies, to a complete system ready for clinical trials. BWL utilizes pressure waves of 390 kHz frequency in 20-cycle bursts to crumble renal calculi by progressively opening up microcracks in the stone material. Compared with extracorporeal shockwave lithotripsy (SWL), BWL may provide an office-based modality for stone management solely driven by ultrasonic (US) technologies to image, fragment, and reposition stones in the kidney. In this in vitro study,3 the authors confirm that 5–7 mm kidney stones of various compositions can be comminuted within 30 minutes in tissue phantoms under clinically relevant test environments. Moreover, the potential of US propulsion combined with B-mode imaging is demonstrated for assessing the treatment endpoint.
Although US imaging is beneficial for treatment guidance and monitoring in BWL, the main challenge in the clinical translation of this novel technology may also hinge on the achievable image quality in human patients with potentially complex body habitus. Compared with the turnkey operation of SWL guided by C-arm fluoroscopy, BWL will require extensive training and practice beyond what is demonstrated in this in vitro study. Furthermore, the operational parameter space (peak negative pressure, pulse repetition frequency, and cycles) of BWL is tightly defined so far, which may need to be carefully expanded to account for the large variations in patient size, stone location, tissue attenuation, and available acoustic windows. More importantly, technological advances in real-time US monitoring of cavitation activities in the renal parenchyma and collecting system from 2D to 3D will be crucial for ensuring the safety and efficacy of BWL in patients, as envisioned for SWL.4
Funding Information
The author's research in lithotripsy has been supported by NIH through Grants R37-DK052985-23 and P20-DK123970-01.
References
- 1. Maxwell AD, Cunitz BW, Kreider W, et al. Fragmentation of renal calculi in vitro by focused ultrasound bursts. J Urol 2015;193:338–344 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Maxwell AD, Wang YN, Kreider W, et al. Evaluation of renal stone comminution and injury by burst wave lithotripsy in a pig model. J Endourol 2019;33:787–792 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3. Ramesh S, Chen TT, Maxwell AD, et al. In vitro evaluation of urinary stone comminution with a clinical burst wave lithotripsy system. J Endourol 2020;34:1167–1173 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4. Zhong P. Shock wave lithotripsy. In: C.F. Delale (Ed.) Bubble Dynamics and Shock Waves. New York: Springer, 2013, pp. 291–338 [Google Scholar]