Chapter

Determination of B/A of Biological Media by Measuring and Modeling Nonlinear Distortion of Pulsed Acoustic Wave in Two-Layer System of Media

DOI: 10.1007/978-90-481-3255-3_34

ABSTRACT Knowledge of the acoustic nonlinearity parameter, B/A, of biological fluids or soft tissues is necessary whenever high intensity pressure fields are induced. A numerical model
recently developed in our lab is capable of fast predicting the nonlinear distortion of pulsed finite-amplitude acoustic waves
generated from axisymmetric sources propagating through multilayer attenuating media. Quantitative analysis of the obtained
results enabled developing the alternative method for determination of the B/A of biological media. First, the method involves measuring the nonlinear waveform distortion of the tone burst propagating
through water. Then, it involves numerical modeling (in frequency domain) using the Time-Averaged Wave Envelope (TAWE) approach.
The numerical simulation results are fitted to the experimental data by adjusting the source boundary conditions to determine
accurately the source pressure, effective radius and apodization function being the input parameters to the numerical solver.
Next, the method involves measuring the nonlinear distortion of idem tone burst passing through the two-layer system of parallel
media. Then, we numerically model nonlinear distortion in two-layer system of media in frequency domain under experimental
boundary conditions. The numerical simulation results are fitted to the experimental data by adjusting the B/A value of the tested material. Values of the B/A for 1.3-butanediol at both the ambient (25°C) and physiological (36.6°C) temperatures were determined. The obtained result (B/A = 10.5 ± 5% at 25°C) is in a good agreement with that available in literature. The B/A = 11.5 ± 5% at 36.6°C was determined.

KeywordsNonlinearity parameter measurement-
B/A
-Nonlinear propagation-Biological media-PVDF membrane hydrophone

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Available from: Janusz Wójcik, Oct 14, 2014
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    • "Then the focal plane occurs within the tissue sample. In previous publications [2] [3] have been shown that for any circular transducer with ka >>1 and weak to moderate source pressure level the axial distance z 1 at which sudden growth of the second harmonics begins (for the tone burst generated from that transducer in water and propagating there) is specific for that transducer and constant independently on the source pressure amplitude. The weak to moderate source level means that in the nonlinear acoustic field produced by the source in water the ratio of the shock formation distance l D to the Rayleigh distance R 0 is larger than about 0.3 [4]. "
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    03/2010; DOI:10.1063/1.3367179
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