Acoustic Characterization of Contrast Agents for Medical Ultrasound Imaging

Hoff, Lars

doi:10.1007/978-94-017-0613-1

Cited by 159 publications

(173 citation statements)

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“…22–24 Therefore, it was assumed that the gas cores of the microbubbles were filled purely with air due to the washing and conjugation steps in air-saturated media. The polytropic exponent for the gas core was calculated by first considering the thermal diffusion length: 6

l_{D} = \sqrt{\frac{K_{g}}{2 ω_{d} ρ_{g} C_{p}}}

where ω d is the damped angular frequency, and K g , ρ g and C p are the thermal conductivity, density and heat capacity at constant pressure of the gas, respectively. The polytropic exponent was then calculated by the following equation: 6

κ = normalRe {{[\frac{1}{γ} (1 + \frac{3 (γ - 1)}{{normalΨ}^{2}} (normalΨ normalcoth normalΨ - 1))]}^{- 1}}

where

normalΨ = \frac{1}{2} (1 + i) \frac{R}{l_{D}}

and γ is the adiabatic constant (specific heat ratio) of the gas.…”

Section: Resultsmentioning

confidence: 99%

“…After measuring and recording a microbubble radius-time curve, the damped resonance frequency was determined using the fast Fourier transform (FFT). The radial oscillations of the microbubble were assumed to obey a linear equation of motion: 6

\overset{x}{true} + 2 δ ω_{0} \overset{x}{true} + {ω_{0}}^{2} x = 0

where

x

is the microbubble radial displacement,

\overset{x}{true}

is the radial velocity,

\overset{x}{true}

is the radial acceleration, δ is the damping ratio, and ω 0 is the angular eigenfrequency. It was also assumed that, after the initial thermal expansion from the pulsed laser heating of the gold nanoparticles, there is no forcing term present during the microbubble oscillations.…”

Section: Methodsmentioning

confidence: 99%

“…4 The stability and dynamic behavior of such acoustic drops and bubbles depends on the lipid monolayer compression rheology. 5,6 In these applications, and others employing microscale drops and bubbles, the relevant timescale for monolayer compression and expansion is given by the eigenfrequency for volumetric oscillations, which typically occurs in the megahertz range. 5–7 …”

Section: Introductionmentioning

confidence: 99%

“…14 This allows one to resolve sub-nanometer scale radial oscillations, or less than ~0.1% area strain, which is well within the linear regime. 6 The intermolecular lipid displacements at such tiny strains are only ~0.1 – 1.0 pm. Thus, the method can approximately measure the intermolecular forces between lipids.…”

Section: Introductionmentioning

confidence: 99%

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Single Microbubble Measurements of Lipid Monolayer Viscoelastic Properties for Small-Amplitude Oscillations

et al. 2016

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Lipid monolayer rheology plays an important role in a variety of interfacial phenomena, the physics of biological membranes, and the dynamic response of acoustic bubbles and drops. We show here measurements of lipid monolayer elasticity and viscosity for very small strains at megahertz frequency. Individual plasmonic microbubbles of 2-6 μm radius were photothermally activated with a short laser pulse, and the subsequent nanometer-scale radial oscillations during ring-down were monitored by optical scatter. This method provided average dynamic response measurements of single microbubbles. Each microbubble was modeled as an underdamped, linear oscillator to determine the damping ratio and eigenfrequency, and thus the lipid monolayer viscosity and elasticity. Our non-isothermal measurement technique revealed viscoelastic trends for different lipid shell compositions. We observed a significant increase in surface elasticity with lipid acyl chain length for 16 to 20 carbons, and this effect was explained by an intermolecular forces model that accounts for lipid composition, packing and hydration. The surface viscosity was found to be equivalent for these lipid shells. We also observed an anomalous decrease in elasticity and increase in viscosity when increasing the acyl chain length from 20 to 22 carbons. These results illustrate the use of a novel nondestructive optical technique to investigate lipid monolayer rheology in new regimes of frequency and strain, possibly elucidating phase behavior, as well as how the dynamic response of a microbubble can be tuned by the lipid intermolecular forces.

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l_{D} = \sqrt{\frac{K_{g}}{2 ω_{d} ρ_{g} C_{p}}}

κ = normalRe {{[\frac{1}{γ} (1 + \frac{3 (γ - 1)}{{normalΨ}^{2}} (normalΨ normalcoth normalΨ - 1))]}^{- 1}}

where

normalΨ = \frac{1}{2} (1 + i) \frac{R}{l_{D}}

and γ is the adiabatic constant (specific heat ratio) of the gas.…”

Section: Resultsmentioning

confidence: 99%

\overset{x}{true} + 2 δ ω_{0} \overset{x}{true} + {ω_{0}}^{2} x = 0

where

x

is the microbubble radial displacement,

\overset{x}{true}

is the radial velocity,

\overset{x}{true}

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Single Microbubble Measurements of Lipid Monolayer Viscoelastic Properties for Small-Amplitude Oscillations

et al. 2016

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show abstract

“…A model for the oscillation of gas bubbles encapsulated in a thin shell [11,12] has been employed to calculate the nonlinear scattering of Sonazoid microbubbles. Sonazoid is a lipid stabilized suspension of perfluorobutane microbubbles with a median diameter between 2.4 and 3.5 micrometers.…”

Section: Resultsmentioning

confidence: 99%

Subharmonic performance of contrast microbubbles: an experimental and numerical investigation

Shi

Hoff²,

Forsberg³

2002 IEEE Ultrasonics Symposium, 2002. Proceedings.

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The diagnostic capabilities of ultrasound imaging can be improved with contrast-specific nonlinear imaging modalities such as harmonic and subharmonic imaging. The subharmonic performance of the ultrasound contrast agent Sonazoid@ (Amersham Health, Oslo, Norway) has been investigated experimentally and numerically for the implementation of subharmonic imaging. Strong subharmonic responses were observed fiom Sonazoid microbubbles in vitro, in vivo and numerically. In conclusion, the scattered subharmonic signal amplitude increases with the total energy w i t h i n each insonation pulse and depends strongly on the polarity of short insonation pulses.

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Ultrasonic Imaging

Kripfgans¹

2006

Encyclopedia of Medical Devices and Instrumentation

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Ultrasonic imaging is one technique for collecting anatomical and physiological information from within the human body. It can be used for diagnosis (imaging) and for image‐guided therapy, where therapeutic intervention can be applied with direct image‐based feedback. Other modalities include X ray (roentgen radiation), CT (computed tomography), MRI (magnetic resonance imaging), PET or PET/CT (positron emission tomography), and SPECT (single photon emission computed tomography). In contrast to most other imaging techniques, ultrasonic imaging is very attractive to professionals because it is cheap, real time (with >100 full frame images per second, >100 Hz), and it uses nonionizing radiation. Moreover, current clinical ultrasound machines can be integrated into laptop computers with very little external hardware for maximum portability and versatility. These combined features allow the use of ultrasonic imaging in a wide variety of settings, from private physician practices, to ambulances with on‐site paramedics, to battle field situations, where very robust and lightweight equipment is required.

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Acoustic Characterization of Contrast Agents for Medical Ultrasound Imaging

Cited by 159 publications

References 0 publications

Single Microbubble Measurements of Lipid Monolayer Viscoelastic Properties for Small-Amplitude Oscillations

Single Microbubble Measurements of Lipid Monolayer Viscoelastic Properties for Small-Amplitude Oscillations

Subharmonic performance of contrast microbubbles: an experimental and numerical investigation

Ultrasonic Imaging

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