Development of optical coherence tomography (OCT) and its applications: Doppler OCT, combined OCT and two-photon microscopy (TPM)

Abstract

Functional and multimodal optical coherence tomography (OCT) is attractive because it combines different contrast mechanisms to provide comprehensive anatomical and functional information of biological tissues. In first topic, we discuss Doppler OCT which combines the Doppler principle with OCT to obtain high-resolution tomographic images of tissue structure and blood flow simultaneously. We demonstrate a high-speed phase-resolved Doppler OCT system for high-sensitivity flow measurements. The minimum detectable velocity of 0.65mm/s with sample signal-to-noise ratio (SNR) below 35dB was achieved. The capabilities of the phase-resolved Doppler OCT system are demonstrated by imaging an Intralipid flow phantom and rat jugular-femoral bypass tube in situ. The combination of OCT and TPM system is introduced in the next topic. This combined system is useful in conducting in-vivo tissue studies, because they provide complementary information regarding tissues. In this thesis, we developed a new combined system using separate light sources and scanners for individually optimal imaging conditions. TPM used a Ti-Sapphire laser and provided molecular and cellular information in microscopic tissue regions. Meanwhile, OCT used a wavelength-swept source centered at 1300 nm and provided structural information in larger tissue regions than TPM. The system was designed to do simultaneous imaging by combining light from both sources. This combined system was tested with simple microsphere specimens, and was then applied to image small intestine and ear tissues of mouse models ex-vivo and plant leaves.