An attempt to reconstruct the lithotriptor shock wave pulse in kidney: possible temperature effects.
Based on measurements carried out in water in two lithotriptor systems, the authors have made an attempt to reconstruct numerically amplitudes and shapes of shock wave pulses penetrating into kidney which differ from those in water. The difference between these pulses and those observed in water was analyzed and was also demonstrated experimentally. The amplitude and the steepness of the reconstructed pulse front were shown to be much lower than in water depending on the distance of the kidney stone from the patient's body surface. For a distance equal to 4 cm, the shock wave pulse amplitude of 40 MPa in water was estimated to decrease in the kidney by a factor of about two and the steepness of the positive shock pulse front to decrease several times. The analysis was carried out by considering the possible changes of absorption and attenuation in tissues which increase in an unknown way with the wave amplitude. It was shown that the temperature elevation caused by the increase of nonlinear high amplitude absorption is limited due to a corresponding increase in attenuation of the shock wave penetrating soft tissues. The temperature elevation was estimated on the basis of this work to be at most 1.8 times that one estimated in the case of two considered lithotripsy systems when assuming small amplitude absorption and attenuation coefficients.
Filipczyński
L
L
Department of Ultrasonics, Polish Academy of Sciences, Warsaw.
Etienne
J
J
Piechocki
M
M
D000818:Animals; D002417:Cattle; D066298:In Vitro Techniques; D007668:Kidney / Q000502:physiology*; D008096:Lithotripsy / Q000009:adverse effects; D013696:Temperature