Characterization and modeling of acousto-optic signal strengths in highly scattering media

Bengtsson, Alexander; Hill, David; Li, Meng; Di, Mengqiao; Cinthio, Magnus; Erlöv, Tobias; Andersson‐Engels, Stefan; Reistad, Nina; Walther, Andreas; Rippe, Lars; Kröll, Stefan

doi:10.1364/boe.10.005565

Cited by 12 publications

(15 citation statements)

References 37 publications

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“…The intensity patterns obtained ( Fig. 3c) indicate an elliptical cross-section of the so formed waveguide 36 , which is in accordance with the US pressure distribution near the focus of the acoustic cylindrical lens 37,38 . It is notable that in the column-focused US configuration, lower control voltage (V pp = 0.08 V, Fig.…”

Section: Resultssupporting

confidence: 75%

“…It should be noted that by using appropriate transducer arrays for US-IRIS generation, there is no need to enclose the light propagation volume, and this flexibility enables to apply our approach in vivo and non-invasively. As the recent results suggest 38 , the depth, at which the US-induced waveguiding effects could be detected, can be significantly improved upon further improvement of employed filtering.…”

Section: Resultsmentioning

confidence: 98%

“…It is important to note that the mechanisms used in our approach are not relying on light coherence 51 . While previously considered too weak for experiment [51][52][53][54][55] , this particular type of light-US interaction is regaining interest [25][26][27][28]38,[56][57][58] and our approach presents a different viewpoint to enrich the understanding of the complex processes involved. Complete uncovering the mechanism of the waveguiding at low pressures requires further investigation and the development of an appropriate theoretical model.…”

Section: Discussionmentioning

confidence: 99%

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Transversally travelling ultrasound for light guiding deep into scattering media

et al. 2020

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The application of optical methods for tissue diagnosis, activation, and treatment suffers dramatically from the low accessible depths due to strong light scattering in tissues. Here we demonstrate a method to address this issue by utilizing transient ultrasound waves, travelling transversally to the light propagation direction, to guide light into deeper tissue regions. We study the formation of the ultrasound-induced refractive index structures and waveguides using simple ultrasound field configurations and analyze their effects on the propagation of short light pulses. As a proof of concept, we demonstrate using 5 ns pulses of 532 nm light and Intralipid-20%-based phantoms with $$\mu _{\mathrm{s}}^\prime$$ μ s ′ up to 4.5 cm−1 a waveguide supported light intensity increase up to the depths of at least 90 mean free paths.

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Section: Resultssupporting

confidence: 75%

Section: Resultsmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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Transversally travelling ultrasound for light guiding deep into scattering media

et al. 2020

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“…7,[17][18][19] A recent work characterized the strength of the first order of ultrasonic-tagged light using slow light filter detection by diffusion theory calculations and experimental measurements. 20 These approaches underestimate the actual tagging efficiency as they do not account for the tagged light that is frequency modulated at higher orders. Some approaches relying on photorefractive effects detect all the tagged light by the change of untagged light.…”

Section: Introductionmentioning

confidence: 99%

Investigating ultrasound–light interaction in scattering media

et al. 2020

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Significance: Ultrasound-assisted optical imaging techniques, such as ultrasound-modulated optical tomography, allow for imaging deep inside scattering media. In these modalities, a fraction of the photons passing through the ultrasound beam is modulated. The efficiency by which the photons are converted is typically referred to as the ultrasound modulation's "tagging efficiency." Interestingly, this efficiency has been defined in varied and discrepant fashion throughout the scientific literature.Aim: The aim of this study is the ultrasound tagging efficiency in a manner consistent with its definition and experimentally verify the contributive (or noncontributive) relationship between the mechanisms involved in the ultrasound optical modulation process.Approach: We adopt a general description of the tagging efficiency as the fraction of photons traversing an ultrasound beam that is frequency shifted (inclusion of all frequency-shifted components). We then systematically studied the impact of ultrasound pressure and frequency on the tagging efficiency through a balanced detection measurement system that measured the power of each order of the ultrasound tagged light, as well as the power of the unmodulated light component. Results:Through our experiments, we showed that the tagging efficiency can reach 70% in a scattering phantom with a scattering anisotropy of 0.9 and a scattering coefficient of 4 mm −1 for a 1-MHz ultrasound with a relatively low (and biomedically acceptable) peak pressure of 0.47 MPa. Furthermore, we experimentally confirmed that the two ultrasound-induced light modulation mechanisms, particle displacement and refractive index change, act in opposition to each other. Conclusion:Tagging efficiency was quantified via simulation and experiments. These findings reveal avenues of investigation that may help improve ultrasound-assisted optical imaging techniques.

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“…In this context, Photo-Acoustic Imaging (PAI) [8][9][10][11][12] and Acousto-Optic Imaging (AOI) [13,14] have drawn increasing interest over the past decades. They both provide a direct mapping of optical absorption properties of scattering tissues.…”

Section: Introductionmentioning

confidence: 99%

Fourier transform acousto-optic imaging with off-axis holographic detection

et al. 2021

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Acousto-optic (AO) imaging is an in-depth optical imaging technique of highly scattering media. One challenging end-application for this technique is to perform imaging of living biological tissues. Indeed, because it relies on coherent illumination, AO imaging is sensitive to speckle decorrelation occurring on the millisecond timescale. Camera-based detections are well suited for in vivo imaging provided their integration time be lower than those decorrelation time scales. In this work, we present Fourier transform acousto-optic imaging combined with off-axis holography which relies on plane-waves and long-duration pulses. We demonstrate, for the first time, a two-dimensional imaging system fully compatible with in vivo imaging prerequisites. The method is validated experimentally by performing in-depth imaging inside a multiple scattering sample.

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Characterization and modeling of acousto-optic signal strengths in highly scattering media

Cited by 12 publications

References 37 publications

Transversally travelling ultrasound for light guiding deep into scattering media

Transversally travelling ultrasound for light guiding deep into scattering media

Investigating ultrasound–light interaction in scattering media

Fourier transform acousto-optic imaging with off-axis holographic detection

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