Polyvinylidene fluoride membrane hydrophone low-frequency response to medical shockwaves

• Published in: The Journal of the Acoustical Society of America 2011-04, Vol.129 (4_Supplement), p.2677-2677
• Main Authors: Bailey, Michael R., Maxwell, Adam D., Pishchalnikov, Yuri A., Sapozhnikov, Oleg A.
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.3588971

Lithotripsy shockwaves are particularly difficult to measure because of their wide signal bandwidth and large pressures. A polyvinylidene fluoride (PVDF) membrane hydrophone and preamplifier were built and tested. A broad-focus electromagnetic lithotripter was used to calibrate the PVDF hydrophone. A fiber optic probe hydrophone (FOPH) with known impulse response was used as a measurement standard for secondary calibration. A low-frequency circuit model for the PVDF membrane electrodes in an infinite conductive medium was developed. The model response was compared with signals recorded by the FOPH and PVDF hydrophone at different levels of water conductivity ranging from 1 to 1300 μS/cm. Measured waveforms were distorted by high-pass filtering effects of the water conductivity. The model results showed good agreement with the measured waveforms and provided a correction for the system. When the input impedance was altered appropriately or the hydrophone was submerged in a nonconductive fluid, the PVDF and FOPH waveforms appeared nearly identical. The PVDF hydrophone is capable of measuring lithotripsy shockwaves accurately when the low-frequency response is properly taken into account. [Work supported by NIH DK43881, NIH EB007643, and NSBRI through NASA NCC 9-58.]