Design of a miniature in-vivo shock wave hydrophone

The authors discuss the development of a miniature precision acoustic sensor (hydrophone) which would survive in an in-vivo shock-wave field. The immediate application of the device is in improving the safety and efficacy of extracorporeal shock-wave lithotripsy (ESWL) treatment of kidney and gallbladder stones. The hydrophone is designed for insertion into the body using a catheter or biopsy needle, to provide reliable in-vivo acoustic pressure measurements of the ESWL. The research efforts include, (1) theoretical modeling to examine design trade-offs associated with material choice and sensor configuration; (2) prototype construction; and (3) acoustical performance characterization. The results of prototype testing are shown and compared to existing hydrophone designs. Performance differences involve bandwidth, directivity, and survivability under shock-wave exposure. The fundamental difficulty is improving survivability without sacrificing bandwidth or signal fidelity