Finite amplitude method for measuring the nonlinearity parameter B∕A in small-volume samples using focused ultrasound

Abstract

On the basis of finite amplitude and comparative methods, the acoustic nonlinearity parameter BA of a liquid sample of as small as 0.1 ml is measured using an 18.6-MHz focused Gaussian beam. The sample fills the space between a polystyrene plate and a tungsten reflector set about 1 mm apart from each other within the focal region. The sound speed c and attenuation coefficient alpha are determined using the time of flight and the insertion loss of the sound passing through the sample, respectively. The density rho is estimated from the reflection coefficient at the interface between the polystyrene plate and the sample, where the transformation from longitudinal to transverse waves is considered. To compensate for the effect of velocity dispersion on the second harmonic generation, the relative phase of the second harmonic sound is also measured using dual-frequency sound. By summarizing all the linear properties and amplitude data of the second harmonic component in the sound transmitted through the sample, the BA value is finally determined. The measurement is validated through the experiments on nondispersive liquids and weakly dispersive biological samples with known BA values.

Molecular structure dependence of acoustic nonlinearity parameter B/A for silicone oils

“…Owing to the specificity of eye surgery, it is necessary that the B/A parameter should be evaluated safely for small samples. Recently, Saito et al developed a finite amplitude method for imaging the B/A parameter of a sample as small as 0.1 ml using 18.6-MHz focused ultrasound, [19,20] which might enable more opportunities of applications of the B/A imaging technique in clinic.…”

Blood Flow Measurement by the Counter-Crossed Beam Contrast Echo Method

“…In the C-CBCE method, two types of transducers face each other at 180 , so that the nonlinearity parameter ðÞ is minimized because B=A values of biological tissues range from 5 to 10. 12,13) Therefore, the echoes from the microbubbles in the microvascular system are measured with a high SNR, and the distribution of the microvascular system around the hepatic cancer is expected to be efficiently enhanced.…”

Interaction of Bursts as a Detector of Material Inhomogeneity

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