Ultrasound-modulated Optical Phenomena In Scattering Media Driven By A Pulsed Transducer

Ultrasound-modulated optical tomography is an imaging technology which has acousto-optic interaction. In this technique, an ultrasonic wave is focused into a scattering medium to modulate light propagating through the acoustic beam. By monitoring modulated components of the diffuse light, the optical and mechanical properties of tissue could be derived. It shows a promising prospect for biomedical imaging. Once it becomes practicality, it will has clinically applied values such as the early detection and treatment of breast cancers and the monitoring of glucose concentration.But many studies on this technique are simulated experiments, it will be a long time to go before its clinically applied. And the mechanism of acousto-optic interaction, the rule of ultrasound-modulated light transport in bio-tissue as well as the effects on electric field and optical properties when the ultrasonic wave is focused into a scattering medium are still mysteries.In this presentation, we dedicated on the basal study of ultrasound-modulated optical tomography:Firstly, we studied on the theory of light transport in bio-tissue and the Boltzmann Equation, then derived the simply analytical expression of Transport Equation in diffusion theory. The characters and the calculation of pulsed ultrasound were also commented. The primary applications of focused ultrasonic system were discussed here. We summarized the evolution and unresolved problems of ultrasound-modulated optical tomography. The current mechanisms and theoretical elements as well as the methods of this technique were reviewed.Secondly, we observed the ultrasound-modulated optical phenomena in a tissue phantom by a pulsed ultrasound transducer. Then we studied some factors including the diameter of aperture in front of the PMT, the power and the frequency as well the pulse repetition rate of ultrasound which affected the modulated signal and the modulation depth by a theoretical analyzing and experimental demonstrating.Thirdly, we investigated the rule of ultrasound-modulated light transport in scattering media based on our analytic model. And we studied the relation of the modulation depth detected at the surface in experiment (M') and the identical modulation depth in theory (M). Thus, we proved the propagation of ultrasound-modulated light in different scattering media by experimental explore, especially the modulation depth detected at the surface in experiment (M') changes with the distance of transport in phantom.