Abstract
Ultrasound optical tomography (UOT) is an imaging technique based on the acousto-optic effect that can perform optical imaging with ultrasound resolution inside turbid media, and is thus interesting for biomedical applications, e.g. for assessing tissue blood oxygenation. In this paper, we present near background free measurements of UOT signal strengths using slow light filter signal detection. We carefully analyze each part of our experimental setup and match measured signal strengths with calculations based on diffusion theory. This agreement between experiment and theory allows us to assert the deep tissue imaging potential of cm for UOT of real human tissues predicted by previous theoretical studies [Biomed. Opt. Express8, 4523 (2017)] with greater confidence, and indicate that future theoretical analysis of optimized UOT systems can be expected to be reliable.
Highlights
Optical imaging is a tool used in medicine for diagnosis and monitoring of health status of superficial biological tissue, since light provides specific contrast between different tissue types
In this paper we present near background free measurements of acousto-optic signal strengths from highly scattering phantoms, enabled using slow light filters based on Pr3+:Y2SiO5 crystals
The results of a ultrasound optical tomography (UOT) experiment using slow light filters programmed in the absorption profile of Pr3+:Y2SiO5 crystals to discriminate between tagged and untagged photons have been presented
Summary
Optical imaging is a tool used in medicine for diagnosis and monitoring of health status of superficial biological tissue, since light provides specific contrast between different tissue types. UOT using spectral hole-burning filters based on Tm3+:YAG crystals operating at ∼ 800 nm has been demonstrated by the authors of Refs.[5,6,7,8], where e.g. Xu et al imaged absorbers embedded in a 3.2 cm thick chicken breast This filter wavelength is highly relevant for medical imaging since it is within the tissue optical window (∼ 650 − 900 nm), where the penetration depth of light is maximal. When using a more optimal wavelength, simulations have shown that UOT using slow light filters could potentially perform fast (250 ms) imaging of small differences in absorption inside real biological tissue at depths of ∼5 cm in a reflection mode setup [14,15] Such a medical imaging technique would offer interesting diagnostic possibilities, e.g. potentially opening up for real-time imaging of oxygenation level at the frontal part of the heart or other deep-lying organs. This could have a large impact on medical diagnosis, e.g. as a triage tool in the emergency ward, especially considering that ischemic heart disease is the leading cause of death worldwide [16]
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