Design of a miniature in-vivo shock wave hydrophone

Abstract

The purpose of this work is 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 Shockwave Lithotripsy (ESL) treatment of kidney and gallbladder stones. The hydrophone is designed for insertion into the body using a catheter or biopsy needle, in order to provide reliable in-vivo acoustic pressure measurements of ESL. The research efforts to date 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 will be shown, and will be 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.

Progress in medical ultrasound exposimetry

“…In one, previously metallized and spot-poled PVDF film was formed into a hemispherical shell supported by a soft, low-impedance backing [204]. The resultant bulb was mounted on the end of a stainless steel tube, with electrical connection being made via a coaxial cable as in the needle hydrophone.…”

The impact of piezoelectric PVDF on medical ultrasound exposure measurements, standards, and regulations

“…For in vivo measurements of lithotripsy pulses (see Section VII), two modifications of the single-sheet, spot-poled membrane design have been used. In one, previously metallized and spotpoled PVDF film was formed into a hemispherical shell supported by a soft, low impedance backing [129]. The resultant bulb was mounted on the end of a stainless steel tube; electrical connection was made via a coaxial cable as in the needle hydrophone.…”

Chitosan-diaphragm based optical-fiber hydrophone for in-vivo ultrasound measurements

“…However, the needle-type hydrophone needs electrical shielding and more susceptible to the cavitations damages and the destruction effects cause by the shock wave lithotripsy, as the intrinsic properties of the barking material used in the design are similar to kidney stones [3]. In this paper, an extrinsic Fabry-Perot interferometry (EFPI) hydrophone is proposed which inherits best attributes of both needle-type and membrane-type hydrophone.…”

“…The configuration of the sensor is based on the fiber-optic Fabry-Perot interferometry which offers good spatial resolution in the tens of MHz range [1] and robust response. Significant applications of the proposed sensor are in vivo micro-imaging [2], in-vivo lithotripsy measurement [3] or event the laboratory characterization of medical ultrasound sources. In this paper, the performance of the sensor is characterized by comparison with a PVDF needle hydrophone in term of sensitivity, frequency response and directivity.…”