Fracture mechanics model of stone comminution in ESWL and implications for tissue damage.
Focused shock waves administered during extracorporeal shock-wave lithotripsy (ESWL) cause stone fragmentation. The process of stone fragmentation is described in terms of a dynamic fracture process. As is characteristic of all brittle materials, fragmentation requires nucleation, growth and coalescence of flaws, caused by a tensile or shear stress. The mechanisms, operative in the stone, inducing these stresses have been identified as spall and compression-induced tensile microcracks, nucleating at pre-existing flaws. These mechanisms are driven by the lithotripter-generated shock wave and possibly also by cavitation effects in the surrounding fluid. In this paper, the spall mechanism has been analysed, using a cohesive-zone model for the material. The influence of shock wave parameters, and physical properties of stone, on stone comminution is described. The analysis suggests a potential means to exploit the difference between the stone and tissue physical properties, so as to make stone comminution more effective, without increasing tissue damage.
Lokhandwalla
M
M
Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena 91125, USA.
Sturtevant
B
B
D002129:Calcium Oxalate; D006801:Humans; D007668:Kidney / Q000473:pathology; D007669:Kidney Calculi / Q000628:therapy*; D008096:Lithotripsy / Q000379:methods*; D008954:Models, Biological; D015233:Models, Statistical; D013997:Time Factors; D014867:Water
D014867:Water; D002129:Calcium Oxalate