Spatial resolution of ultrasound-modulated optical tomography used for the detection of absorbing and scattering objects in thick scattering media

摘要

Ultrasound-modulated optical tomography (UOT) combines the spatial resolution of ultrasonic waves and the spectroscopic properties of light to detect optically absorbing and/or scattering objects in highly scattering media. In this work, a double-pass confocal Fabry-Perot interferometer is used as a bandpass filter to selectively detect the ultrasound-tagged photons. The limited etendue of the confocal Fabry-Perot interferometer is compensated by using a single-frequency laser emitting high-peak-power optical pulses. Compared to photoacoustic tomography, UOT is not only sensitive to optical absorption but also to scattering properties. In this paper, we consider the detection of absorbing and scattering objects embedded in thick (30 to 60 mm) tissue-mimicking phantoms and biological tissues. The experimental evaluation of the spatial resolution of the technique is compared to that expected from the ultrasonic beam intensity profile. Preliminary results indicate that the edge spread function is influenced by the level of absorption of the embedded object.