Tracking shear waves in turbid medium by light: theory, simulation, and experiment

Li, Sinan; Yi, Chunhui; Song, Lipei; Eckersley, Robert J.; Elson, Daniel S.; Tang, Meng‐Xing

doi:10.1364/ol.39.001597

Cited by 9 publications

(7 citation statements)

References 18 publications

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“…Using this experimental setup, we were able to demonstrate and quantify the effects of ultrasound modulation on incoherent light, and here we report experimental evidence that the ultrasound focal zone produces a spatial variation of light absorption which, when projected, replicates the expected distribution of sound pressure and material density in the sound field. This effect differs from previous reports of diffraction phenomena caused by phase differences such as those mentioned above, and allows a much simpler approach to the observation of sound fields than those provided by previous work [29]–[32].…”

Section: Introductioncontrasting

confidence: 67%

Detection of a Novel Mechanism of Acousto-Optic Modulation of Incoherent Light

2014

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A novel form of acoustic modulation of light from an incoherent source has been detected in water as well as in turbid media. We demonstrate that patterns of modulated light intensity appear to propagate as the optical shadow of the density variations caused by ultrasound within an illuminated ultrasonic focal zone. This pattern differs from previous reports of acousto-optical interactions that produce diffraction effects that rely on phase shifts and changes in light directions caused by the acoustic modulation. Moreover, previous studies of acousto-optic interactions have mainly reported the effects of sound on coherent light sources via photon tagging, and/or the production of diffraction phenomena from phase effects that give rise to discrete sidebands. We aimed to assess whether the effects of ultrasound modulation of the intensity of light from an incoherent light source could be detected directly, and how the acoustically modulated (AOM) light signal depended on experimental parameters. Our observations suggest that ultrasound at moderate intensities can induce sufficiently large density variations within a uniform medium to cause measurable modulation of the intensity of an incoherent light source by absorption. Light passing through a region of high intensity ultrasound then produces a pattern that is the projection of the density variations within the region of their interaction. The patterns exhibit distinct maxima and minima that are observed at locations much different from those predicted by Raman-Nath, Bragg, or other diffraction theory. The observed patterns scaled appropriately with the geometrical magnification and sound wavelength. We conclude that these observed patterns are simple projections of the ultrasound induced density changes which cause spatial and temporal variations of the optical absorption within the illuminated sound field. These effects potentially provide a novel method for visualizing sound fields and may assist the interpretation of other hybrid imaging methods.

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Section: Introductioncontrasting

confidence: 67%

Detection of a Novel Mechanism of Acousto-Optic Modulation of Incoherent Light

2014

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“…al developed a method to quantitatively measure the elasticity [19] and viscosity [20] at 1.2 cm depth in an optically turbid medium by tracking ARF-generated shear wave propagation using laser speckle contrast analysis. A systemic description of the theory, simulation and experiment can be found in [21]. This work opened up the possibility of a dual-contrast imaging tool at a clinical useful depth.…”

Section: Introductionmentioning

confidence: 95%

“…The theory and simulation of shear wave tracking with coherent light and speckle contrast detection are described in [21]. The interaction between shear waves and light is simulated by coupling the analytic shear wave solution [1] with the multiply scattered photon trajectories predicated by the Monte Carlo modelling [23].…”

Section: Simulationmentioning

confidence: 99%

“…the method in [19] tracking a single shear wave, suffer from inaccurate estimation of shear wave speed near elastic boundaries due to shear wave reflections. Also, despite being a highly sensitive method for shear wave tracking (sensible to tens of nanometres displacement at cm-depth [21]), tissue movement in vivo may cause a reduction of the signalto-noise ratio (SNR) due to speckle decorrelation. This manuscript reports the observation of two counter-propagating shear wave interaction using laser speckle contrast detection and its improvement in shear wave speed measurement by reducing the above effects.…”

Section: Introductionmentioning

confidence: 99%

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Dual shear wave induced laser speckle contrast signal and the improvement in shear wave speed measurement

Eckersley

et al. 2015

Biomed. Opt. Express

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Shear wave speed is quantitatively related to tissue viscoelasticity. Previously we reported shear wave tracking at centimetre depths in a turbid optical medium using laser speckle contrast detection. Shear wave progression modulates displacement of optical scatterers and therefore modulates photon phase and changes the laser speckle patterns. Time-resolved charge-coupled device (CCD)-based speckle contrast analysis was used to track shear waves and measure the time-of-flight of shear waves for speed measurement. In this manuscript, we report a new observation of the laser speckle contrast difference signal for dual shear waves. A modulation of CCD speckle contrast difference was observed and simulation reproduces the modulation pattern, suggesting its origin. Both experimental and simulation results show that the dual shear wave approach generates an improved definition of temporal features in the time-of-flight optical signal and an improved signal to noise ratio with a standard deviation less than 50% that of individual shear waves. Results also show that dual shear waves can correct the bias of shear wave speed measurement caused by shear wave reflections from elastic boundaries.

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“…In [17], shear waves were generated a distance away from the laser axis. The propagation of shear waves to the optical detection volume increases the displacement of optical scatterers and thus the speckle contrast difference (∆C) recorded by a CCD camera [18]. The time-to-peak of the timeresolved CCD speckle contrast difference signal ∆C(t) indicates the time-of-flight of shear waves.…”

Section: Introductionmentioning

confidence: 99%

Detecting tissue optical and mechanical properties with an ultrasound modulated optical imaging system in reflection detection geometry

Eckersley

et al. 2014

Biomed. Opt. Express

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Tissue optical and mechanical properties are correlated to tissue pathologic changes. This manuscript describes a dual-mode ultrasound modulated optical imaging system capable of sensing local optical and mechanical properties in reflection geometry. The optical characterisation was achieved by the acoustic radiation force assisted ultrasound modulated optical tomography (ARF-UOT) with laser speckle contrast detection. Shear waves generated by the ARF were also tracked optically by the same system and the shear wave speed was used for the elasticity measurement. Tissue mimicking phantoms with multiple inclusions buried at 11 mm depth were experimentally scanned with the dual-mode system. The inclusions, with higher optical absorption and/or higher stiffness than background, were identified based on the dual results and their stiffnesses were quantified. The system characterises both optical and mechanical properties of the inclusions compared with the ARF-UOT or the elasticity measurement alone. Moreover, by detecting the backward scattered light in reflection detection geometry, the system is more suitable for clinical applications compared with transmission geometry.

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Tracking shear waves in turbid medium by light: theory, simulation, and experiment

Cited by 9 publications

References 18 publications

Detection of a Novel Mechanism of Acousto-Optic Modulation of Incoherent Light

Detection of a Novel Mechanism of Acousto-Optic Modulation of Incoherent Light

Dual shear wave induced laser speckle contrast signal and the improvement in shear wave speed measurement

Detecting tissue optical and mechanical properties with an ultrasound modulated optical imaging system in reflection detection geometry

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