Image not available

Lautz J et al, 2013: Turbulent water coupling in shock wave lithotripsy

Lautz J, Sankin G, Zhong P
Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708, USA


Abstract

Previous studies have demonstrated that stone comminution decreases with increased pulse repetition frequency as a result of bubble proliferation in the cavitation field of a shock wave lithotripter (Pishchalnikov et al 2011 J. Acoust. Soc. Am. 130 EL87-93). If cavitation nuclei remain in the propagation path of successive lithotripter pulses, especially in the acoustic coupling cushion of the shock wave source, they will consume part of the incident wave energy, leading to reduced tensile pressure in the focal region and thus lower stone comminution efficiency. We introduce a method to remove cavitation nuclei from the coupling cushion between successive shock exposures using a jet of degassed water. As a result, pre-focal bubble nuclei lifetime quantified by B-mode ultrasound imaging was reduced from 7 to 0.3 s by a jet with an exit velocity of 62 cm s(-1). Stone fragmentation (percent mass <2 mm) after 250 shocks delivered at 1 Hz was enhanced from 22 ± 6% to 33 ± 5% (p = 0.007) in water without interposing tissue mimicking materials. Stone fragmentation after 500 shocks delivered at 2 Hz was increased from 18 ± 6% to 28 ± 8% (p = 0.04) with an interposing tissue phantom of 8 cm thick. These results demonstrate the critical influence of cavitation bubbles in the coupling cushion on stone comminution and suggest a potential strategy to improve the efficacy of contemporary shock wave lithotripters.

Phys Med Biol. 2013 Feb 7;58(3):735-48. doi: 10.1088/0031-9155/58/3/735. Epub 2013 Jan 15
PMID:23322027 [PubMed - in process]

Rate this blog entry:
0
 

Comments 1

Hans-Göran Tiselius on Monday, 06 May 2013 07:42

This is indeed a highly interesting report, the results of which might be important for further improvements of the SWL technology. The authors showed experimentally that the development and presence of cavitation bubbles in the water coupling medium significantly reduced the tensile pressure of the shock wave by reducing the cavitation effect in the focal volume. By using a jet-flow in the water compartment, the life-time of cavitation bubbles could be reduced from approx. 7s to 0.3 s. This means that the disintegrating power remains unaffected even with a shock wave frequency as high as 2 Hz.

It will be very interesting to see what this method to suppress cavitation bubbles in the water transmission medium can have on the clinical outcome in terms of stone disintegration, tissue effects and treatment time.

Hans-Göran Tiselius

This is indeed a highly interesting report, the results of which might be important for further improvements of the SWL technology. The authors showed experimentally that the development and presence of cavitation bubbles in the water coupling medium significantly reduced the tensile pressure of the shock wave by reducing the cavitation effect in the focal volume. By using a jet-flow in the water compartment, the life-time of cavitation bubbles could be reduced from approx. 7s to 0.3 s. This means that the disintegrating power remains unaffected even with a shock wave frequency as high as 2 Hz. It will be very interesting to see what this method to suppress cavitation bubbles in the water transmission medium can have on the clinical outcome in terms of stone disintegration, tissue effects and treatment time. Hans-Göran Tiselius
Guest
Tuesday, 26 September 2017
STORZ MEDICAL AG
Lohstampfestrasse 8
8274 Tägerwilen
Switzerland
Tel.: +41 (0)71 677 45 45
Fax: +41 (0)71 677 45 05

www.storzmedical.com
Personal data
Address
Contact data
Message