Effect of the diameter and the sound speed of a kidney stone on the acoustic field induced by shock waves

A time-domain finite-difference solution to the acoustic wave equation was used to model the propagation of lithotripsy shock waves in kidney stones. Varying the sound-speed of the stone had minimal effect on the pressure within the stone. Reducing stone diameter dramatically reduced negative, but not positive, pressures. For composite stones the pressures amplitude changed little, but specific configurations resulted in the peak negative pressure occurring at an internal interface-a likely weak point in the stone. These results indicate that the pressure field in a kidney stone is very sensitive to the size and internal composition of the stone. (C) 2004 Acoustical Society of America.