Rassweiler JJ et al, 2011: Shock wave technology and application: an update
Rassweiler JJ, Knoll T, Köhrmann KU, McAteer JA, Lingeman JE, Cleveland RO, Bailey MR, Chaussy C.
Department of Urology, Klinikum Heilbronn, SLK Kliniken Heilbronn, University of Heidelberg, Heilbronn, Germany.
CONTEXT: The introduction of new lithotripters has increased problems associated with shock wave application. Recent studies concerning mechanisms of stone disintegration, shock wave focusing, coupling, and application have appeared that may address some of these problems.
OBJECTIVE: To present a consensus with respect to the physics and techniques used by urologists, physicists, and representatives of European lithotripter companies.
EVIDENCE ACQUISITION: We reviewed recent literature (PubMed, Embase, Medline) that focused on the physics of shock waves, theories of stone disintegration, and studies on optimising shock wave application. In addition, we used relevant information from a consensus meeting of the German Society of Shock Wave Lithotripsy.
EVIDENCE SYNTHESIS: Besides established mechanisms describing initial fragmentation (tear and shear forces, spallation, cavitation, quasi-static squeezing), the model of dynamic squeezing offers new insight in stone comminution. Manufacturers have modified sources to either enlarge the focal zone or offer different focal sizes. The efficacy of extracorporeal shock wave lithotripsy (ESWL) can be increased by lowering the pulse rate to 60-80 shock waves/min and by ramping the shock wave energy. With the water cushion, the quality of coupling has become a critical factor that depends on the amount, viscosity, and temperature of the gel. Fluoroscopy time can be reduced by automated localisation or the use of optical and acoustic tracking systems. There is a trend towards larger focal zones and lower shock wave pressures.
CONCLUSIONS: New theories for stone disintegration favour the use of shock wave sources with larger focal zones. Use of slower pulse rates, ramping strategies, and adequate coupling of the shock wave head can significantly increase the efficacy and safety of ESWL.
Copyright © 2011 European Association of Urology. Published by Elsevier B.V. All rights reserved.
Eur Urol. 2011 May;59(5):784-96. doi: 10.1016/j.eururo.2011.02.033. Epub 2011 Feb 23
PMID: 21354696 [PubMed - in process]. FREE ARTICLE
This is the third publication on the current status of lithotripter technology published by Rassweiler et al. in European Urology since 2001. The ease with which extracorporeal lithotripsy can be performed leads to an increased tendency of the users to regard the lithotripter as a machine whose function must not necessarily be understood. The up-to-date insight into lithotripter technology will help users to better understand what they are doing, increase the quality of treatment and probably stimulate further research in that field.