Method and Apparatus to Detect the Fragmentation of Kidney Stones by Measuring Acoustic Scatter

Abstract

During shock wave therapy, a determination is made that a kidney stone has begun to fracture, and then to assess a progress of its fragmentation. This determination can reduce the number of shock waves used to disintegrate kidney stones, and thereby reduce dose-dependent tissue damage. The identification of fracture is possible through the detection and analysis of resonant acoustic scattering, which is the radiation caused by reverberations within a stone particle that is stuck by a shock wave. The scattering frequency can provide both an indication that the kidney stone has fragmented, and an indication of the relative sizes of the fragments. Related concepts employ displacement measurements of kidney stones/fragments to provide both an indication that the kidney stone has fragmented, and an indication of the relative sizes of the fragments. Such techniques can be combined with vibro-acoustography based gating that better targets the stone.

1 . (canceled) 
     
     
         2 . A method for treating a kidney stone, comprising applying an acoustic pressure pulse to one or more kidney stone fragments, wherein the acoustic pressure pulse applied is effective to disperse the one or more kidney stone fragments to facilitate removal of the one or more kidney stone fragments from the kidney. 
     
     
         3 . The method of  claim 2 , wherein prior to applying the acoustic pressure pulse, the method further comprises fragmenting the kidney stone. 
     
     
         4 . The method of  claim 3 , wherein fragmenting the kidney stone comprises administering a plurality of shock waves to the kidney stone, wherein the plurality of shock waves applied are effective to fragment the kidney stone. 
     
     
         5 . The method of  claim 4 , wherein the steps of (i) administering the plurality of shock waves to the kidney stone, and (ii) applying the acoustic pressure pulse to one or more kidney stone fragments, are cyclically carried out two or more times. 
     
     
         6 . The method of  claim 2 , wherein the acoustic pressure pulse is generated by an ultrasound probe. 
     
     
         7 . The method of  claim 6 , wherein the ultrasound probe is an ultrasound imaging probe or a Doppler ultrasound probe. 
     
     
         8 . The method of  claim 4 , wherein the acoustic pressure pulse is generated by an acoustic pressure source disposed along a shock wave axis of the plurality of shock waves. 
     
     
         9 . The method of  claim 4 , wherein the acoustic pressure pulse is generated by an acoustic pressure source disposed at an angle relative to a shock wave axis of the plurality of shock waves. 
     
     
         10 . The method of  claim 3 , wherein the method further comprises detecting kidney stone fragmentation. 
     
     
         11 . The method of  claim 10 , wherein detecting fragmenting of the kidney stone comprises
 (a) detecting a resonant acoustic scattering wave to generate a resonant acoustic scattering signal, the resonant acoustic scattering signal being indicative of internal stress vibrations in the kidney stone, where the internal stress vibrations are in response to shock waves impacting the kidney stone;   (b) processing the resonant acoustic scattering signal to determine a frequency spectrum of the stress vibrations, the processing comprising determining a frequency spectrum of the stress vibrations induced by an initial shock wave, and determining a frequency spectrum of the stress vibrations induced by at least one subsequent shock wave; and   (c) monitoring the frequency spectrum of the stress vibrations during therapy in order to detect kidney stone fragmentation.   
     
     
         12 . The method of  claim 11 , wherein the monitoring comprises comparing the frequency spectrum of the stress vibrations induced by the initial shock wave with the frequency spectrum of the stress vibrations induced by the at least one subsequent shock wave to detect a change in the frequency spectrum, the change in the frequency spectrum being indicative of kidney stone fragmentation. 
     
     
         13 . A system, comprising
 (a) a processor;   (b) an acoustic pressure source; and   (c) a non-transitory computer-readable medium configured to store program instructions that, when executed by the processor, cause the system to carry out the method of  claim 1 .   
     
     
         14 . The system of  claim 13  wherein the acoustic pressure source is an ultrasound probe. 
     
     
         15 . The system of  claim 13 , wherein the ultrasound probe is an ultrasound imaging probe or a Doppler ultrasound probe. 
     
     
         16 . The system of  claim 13 , further comprising a shock wave source, wherein the non-transitory computer-readable medium is configured to store program instructions that, when executed by the processor, cause the system to administer a plurality of shock waves to the kidney stone, wherein the plurality of shock waves applied are effective to fragment the kidney stone. 
     
     
         17 . The system of  claim 16 , wherein the shock wave source is an ultrasound probe.