Method to reduce tissue injury in shock wave lithotripsy

A method for comminuting with reduced tissue injury a concretion located within a living body, said method consisting essentially of the steps of:

• (a) creating a multi-pulsed shock wave by an acoustic source, said acoustic source having an axis, said multi-pulsed shock wave consisting of a leading acoustic shock wave pulse and a weaker second acoustic shock wave pulse;
• (b) focusing said leading acoustic shock wave pulse to a secondary focus and focusing said second acoustic shock wave pulse to a primary focus where said concretion is located, said primary focus and said secondary focus are aligned on said axis of said acoustic source, said secondary focus being closer than said primary focus to said acoustic source by a distance of less than 24 millimeters, said first and second acoustic shock wave pulses thereby being separated in arrival time at said primary focus by an interpulse delay between 0.5 and 21 microseconds, said leading acoustic shock wave pulse upon its arrival at said primary focus having a compressive pressure amplitude of at least 10 megapascals and having a tensile pressure amplitude of at least 0.5 megapascals to produce an inertial cavitation bubble cluster, said inertial bubble cluster embracing said concretion;
• and
• (c) said second acoustic shock wave pulse upon its arrival said primary focus having a compressive pressure amplitude of at least 5 megapascals and having a tensile pressure amplitude of less than 8 megapascals, and said second acoustic shock wave pulse thereby serving to substantially suppress expansion of said inertial cavitation bubble duster induced by said leading acoustic shock wave pulse in tissues surrounding said concretion, whereby said concretion is comminuted with a concomitant reduction in tissue injury.