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

Kajoli B. Krishnan; Pavel Fomitchov; Stephen J. Lomnes; Manohar Kollegal; Floris P. Jansen

doi:10.1117/12.630819

21 November 2005 A theory for the ultrasonic modulation of incoherent light in turbid medium

Kajoli B. Krishnan, Pavel Fomitchov, Stephen J. Lomnes, Manohar Kollegal, Floris P. Jansen

Proceedings Volume 6009, Optical Methods in Drug Discovery and Development; 60090V (2005) https://doi.org/10.1117/12.630819
Event: Optics East 2005, 2005, Boston, MA, United States

Abstract

A diffusion approximation to the radiative transfer in a medium with varying refractive index has been proposed as a theoretical model for the ultrasonic tagging of fluorescence or FluoroSound, in a scattering medium. It has been found that the diffuse modulation is a defocusing effect. Defocusing is related to scatter - more the scatter, more the defocusing and there exists a component of the defocusing effect of scatter at the ultrasonic frequency. This is in contrast to the modulation for ballistic photons that originates in the focusing effect of the acoustic lens created by the ultrasonic wave. Simulations with circular phantoms of 1.5 and 2.0cm radius have shown that defocusing is minimum when the acoustic lens is midway between the source and the detector. These results are consistent with physics and demonstrate the capability of the model to function as a predictive tool for FluoroSound instrument design. Both ballistic and diffuse FluoroSound signatures can help in the simultaneous localization of the anomaly and determination of its optical properties. As an adjunct, optimally designed ultrasound beams can be also used to enhance diffuse photon modulation signal through acoustic guidance. Optical properties provide a way to discriminate between normal and diseased tissue. FluoroSound could therefore potentially achieve a fusion of anatomical and functional information non-invasively in a single measurement. The additional information made available by this method will improve the speed and accuracy of optical imaging as a tool in the identification and validation of targets.

Citation Download Citation

Kajoli B. Krishnan, Pavel Fomitchov, Stephen J. Lomnes, Manohar Kollegal, and Floris P. Jansen "A theory for the ultrasonic modulation of incoherent light in turbid medium", Proc. SPIE 6009, Optical Methods in Drug Discovery and Development, 60090V (21 November 2005); https://doi.org/10.1117/12.630819

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