A theory for the ultrasonic modulation of incoherent light in turbid medium

Krishnan, Kasiraman; Fomitchov, Pavel A.; Lomnes, Stephen J.; Kollegal, Manohar; Jansen, Floris

doi:10.1117/12.630819

Cited by 12 publications

(12 citation statements)

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“…However, this mechanism cannot explain fluorescence modulation because fluorescence radiation in a turbid medium should be considered as incoherent light (see Sec. II for detailed discussions) 3,6,9,10,13. Krishnan et al 3 proposed a model to explain the modulation of fluorescence based on an acoustic lens assumption.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of the ultrasonic modulation of fluorescence in turbid media

Yuan

Gamelin

Zhu

2008

Journal of Applied Physics

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To understand the modulation mechanisms of fluorescence emission induced by ultrasonic waves in turbid media, a mathematical model is proposed and compared with the recent experimental observations of Kobayashi et al. [Appl. Phys. Lett. 89, 181102 (2006)]. Modulation of fluorophore concentration is considered as the source of the oscillation of fluorescence signals when fluorophore concentration is low enough so that quenching effects can be ignored. By solving the rate equation and photon diffusion equation, quantitative solutions are given to quantify the modulation strength. Our calculations predict that the modulation depth (the ratio of the modulated signal strength to the unmodulated signal strength) can reach 10−4 when ultrasonic pressure with the order of magnitude of megapascals is applied in the ultrasound focal zone. Our model explains the relationship between the modulation strength and the average fluorophore concentration and also predicts a method to measure or image fluorescence lifetime in the turbid medium. When fluorophore concentration is high enough so that fluorescence quenching occurs, the fluorescence modulation is attributed to the modulation of quenching efficiency. Quenching caused by fluorescence resonance energy transfer can lead to a nonlinear relationship between the modulation fluorescence strength and the applied ultrasound strength.

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Section: Introductionmentioning

confidence: 99%

Mechanisms of the ultrasonic modulation of fluorescence in turbid media

Yuan

Gamelin

Zhu

2008

Journal of Applied Physics

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“…More recently researchers have reported detection of ultrasound-modulated incoherent photons [11]. Here, the ultrasound modulates the optical properties (refractive index, absorption, scattering) of the ultrasound focal zone resulting in a modulation of the local optical attenuation coefficient causing an in-phase intensity modulation of the photons (be they incoherent or coherent).…”

Section: Introductionmentioning

confidence: 99%

Quadrature Detection of Ultrasound-Modulated Photons with a Gain-Modulated, Image-Intensified, CCD Camera

Hall

Sunar²,

Farshchi-Heydari³

2008

TOOPTSJ

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Acousto-optic imaging promises to provide in vivo images of optical contrast but with the superior spatial resolution of ultrasound imaging. Here we present novel quadrature detection of ultrasound-modulated photons with a gainmodulated, image-intensified, CCD camera. The additional detection of ultrasound-modulated fluorescence photons demonstrates potential for in vivo acousto-optic molecular imaging.

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“…A fairly limited amount of research has been conducted in this area. Much of this has been fundamental, investigating the mechanisms for modulation [10][11][12][13][14] and concentrating on the position of the US focus relative to the fluorescent target. For example, Yuan and colleagues 10,14 and Hall 12 suggested that modulating the excitation beam would be most effective.…”

Section: Introductionmentioning

confidence: 99%

Effect of object size and acoustic wavelength on pulsed ultrasound modulated fluorescence signals

Huynh

Ruan

et al. 2012

J. Biomed. Opt

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Detection of ultrasound (US)-modulated fluorescence in turbid media is a challenge because of the low level of fluorescent light and the weak modulation of incoherent light. A very limited number of theoretical and experimental investigations have been performed, and this is, to our knowledge, the first demonstration of pulsed US-modulated fluorescence tomography. Experimental results show that the detected signal depends on the acoustic frequency and the fluorescent target's size along the ultrasonic propagation axis. The modulation depth of the detected signal is greatest when the length of the object along the acoustic axis is an odd number of half wavelengths and is weakest when the object is an integer multiple of an acoustic wavelength. Images of a fluorescent tube embedded within a 22- by 13- by 30 mm scattering gel phantom (μ(s)∼15 cm(-1), g=0.93) with 1-, 1.5-, and 2 MHz frequency US are presented. The modulation depth of the detected signal changes by a factor of 5 depending on the relative size of the object and the frequency. The approach is also verified by some simple experiments in a nonscattering gel and using a theoretical model.

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A theory for the ultrasonic modulation of incoherent light in turbid medium

Cited by 12 publications

References 0 publications

Mechanisms of the ultrasonic modulation of fluorescence in turbid media

Mechanisms of the ultrasonic modulation of fluorescence in turbid media

Quadrature Detection of Ultrasound-Modulated Photons with a Gain-Modulated, Image-Intensified, CCD Camera

Effect of object size and acoustic wavelength on pulsed ultrasound modulated fluorescence signals

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