Measurement of Broadband Temperature-Dependent Ultrasonic Attenuation and Dispersion Using Photoacoustics

Abstract

The broadband ultrasonic characterization of biological fluids and tissues is important for the continued development and application of high-resolution ultrasound imaging modalities. Here, a photoacoustic technique for the transmission measurement of temperature-dependent ultrasonic attenuation and dispersion is described. The system uses a photoacoustic plane wave source constructed from a polymethylmethacrylate substrate with a thin optically absorbent layer. Broadband ultrasonic waves are generated by illuminating the absorbent layer with nanosecond pulses of laser light. The transmitted ultrasound waves are detected by a planar 7-microm high-finesse Fabry-Perot interferometer. Temperature-induced thickness changes in the Fabry-Perot interferometer are tracked to monitor the sample temperature and maintain the sensor sensitivity. The measured -6 dB bandwidth for the combined source and sensor is 1 to 35 MHz, with an attenuation corrected signal level at 100 MHz of -10 dB. The system is demonstrated through temperature-dependent ultrasound measurements in castor oil and olive oil. Power law attenuation parameters are extracted by fitting the experimental attenuation data to a frequency power law while simultaneously fitting the dispersion data to the corresponding Kramers-Krönig relation. The extracted parameters are compared with other calibration measurements previously reported in the literature.

Measurement of the Ultrasound Attenuation and Dispersion in Whole Human Blood and its Components From 0–70 MHz

“…The flow speed was maintained at 1.7 mL/s for all tests. During circulation, broadband monopolar ultrasound plane wave pulses were continuously generated via thermo-elastic expansion by illuminating an optically absorbing black paint layer on one side of the test cavity with nanosecond laser 292 Ultrasound in Medicine and Biology Volume 37, Number 2, 2011 pulses (Treeby et al 2009). The thickness of the optically absorbing paint layer was sufficient such that the transmission of optical power through the layer was less than 2%.…”

“…The amplitude and phase spectrums were then calculated using a circular-shifted fast Fourier transform as described by Treeby et al (2009). These were used to calculate the attenuation and dispersion within the test fluid.…”

Time-Domain Simulation of Ultrasound Propagation in a Tissue-Like Medium Based on the Resolution of the Nonlinear Acoustic Constitutive Relations

“…The boundary conditions were implemented for a spherical focused ultrasound source. The castor oil parameters at 26 C room temperature 45 , were c 0 = 1480 m/s, ρ 0 = 961 kg/m 3 , α = 0.4 dB/cm/MHz γ , γ = 1.69, B/A = 12.0. The grid parameters were ∆r = ∆z = 29.6 µm and ∆t = 13.6 ns, leading to a CFL number S = 0.95 and N λ = 50 elements per wavelength at fundamental frequency, note that this grid leads to N λ = 16 for third harmonic.…”

Optimization of a label‐free biosensor vertically characterized based on a periodic lattice of high aspect ratio SU‐8 nano‐pillars with a simplified 2D theoretical model

“…The source was completely immersed in a castor oil tank (350× 350 × 350 mm). We select this frequency power law attenuation media due to the low variability of its acoustic properties along existent literature (Liebler et al, 2004;Treeby et al, 2009). Using a sound speed inside the bulk of the lens c l = 2711 m/s, and a sound speed of the castor oil of c 0 = 1480 m/s (at 26 o C room temperature), the effective lens geometrical focal is estimated as F = R/(1 − c 0 /c l ) = 110.1 mm, leading to a linear lossless gain of G = 13.4.…”

“…The boundary conditions were implemented for a spherical focused ultrasound source. The castor oil parameters at 26 o C room temperature (Treeby et al, 2009), were c 0 = 1480 m/s, ρ 0 = 961 kg/m 3 , α = 0.4 dB/cm/MHz γ , γ = 1.69, B/A = 12.0. The grid parameters were ∆r = ∆z = 29.6 µm and ∆t = 13.6 ns, leading to a CFL number S = 0.95 and N λ = 50 elements per wavelength at fundamental frequency, note that this grid leads to N λ = 16 for third harmonic.…”