Abstract
In vivo photothermal optical coherence tomography (OCT) is demonstrated for cross-sectional imaging of endogenous absorption agents. In order to compromise the sensitivity, imaging speed, and sample motion immunity, a new photothermal detection scheme and phase processing method are developed. Phase-resolved swept-source OCT and fiber-pigtailed laser diode (providing excitation at 406 nm) are combined to construct a high-sensitivity photothermal OCT system. OCT probe and excitation beam coaxially illuminate and are focused on tissues. The photothermal excitation and detection procedure is designed to obtain high efficiency of photothermal effect measurement. The principle and method of depth-resolved cross-sectional imaging of absorption agents with photothermal OCT has been derived. The phase-resolved thermal expansion detection algorithm without motion artifact enables in vivo detection of photothermal effect. Phantom imaging with a blood phantom and in vivo human skin imaging are conducted. A phantom with guinea-pig blood as absorber has been scanned by the photothermal OCT system to prove the concept of cross-sectional absorption agent imaging. An in vivo human skin measurement is also performed with endogenous absorption agents.
Highlights
Micro-scale non-invasive cross-sectional imaging of endogenous agents in vivo may attain further level of investigation and diagnosis of diseases
The optical path length (OPL) change due to the photothermal effect is measured by the phase-resolved processing of Optical coherence tomography (OCT) and is disturbed by the bulk tissue motion
A porcine liver has been scanned by the photothermal OCT
Summary
Micro-scale non-invasive cross-sectional imaging of endogenous agents in vivo may attain further level of investigation and diagnosis of diseases. The OPL change due to the photothermal effect is measured by the phase-resolved processing of OCT and is disturbed by the bulk tissue motion. To obtain a cross-sectional depth-resolving absorption contrast, the accumulation of OPL change due to the photothermal effect should be resolved [5, 9, 19, 20]. These hurdles make the in vivo photothermal OCT imaging of endogenous agents challenging. In vivo human skin imaging of endogenous absorption agents is demonstrated
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