Light reflectance of blood is a complex phenomenon affected by hematocrit and red blood cell (RBC) aggregation (rouleaux formation). According to the hypothesis that RBC rouleaux are aligned with the direction of blood flow, the spatial alignment of RBC rouleaux, as well as their size and quantity in the blood, may also affect light reflectance. The present study aims to investigate the effect of the spatial alignment and distribution of RBC rouleaux on light reflection using optical coherence tomography (OCT). Blood flow velocity and reflectance profiles in a rat jugular-femoral bypass loop were simultaneously measured using a Doppler swept-source OCT system at various incident angles from −30 to +30 deg. The reflectance profiles of flowing blood show nonmonotonous decay with a local negative peak at the center of the tube. The profiles vary depending on the incident angle. This angular dependence is stronger at a higher angle of incidence. The anisotropic reflectance of flowing blood is consistent with the hypothesis on the spatial alignment of RBC rouleaux.
Bosu Jeong, Byunghak Lee, Min Seong Jang, Hyoseok Nam, Hae Koo Kim, Sang June Yoon, Junsang Doh, Sang-Joon Lee, Bo-Gie Yang, Myoung Ho Jang, Ki Hean Kim
Two-photon microscopy (TPM) and optical coherence tomography (OCT) are 3D tissue imaging techniques based on
different contrast mechanisms. We developed a combined system of TPM and OCT to provide information of both
imaging modalities for in-vivo tissue study. TPM and OCT were implemented by using separate light sources, a
Ti-Sapphire laser and a wavelength-swept source centered at 1300 nm respectively, and scanners. Light from the two
sources was combined for the simultaneous imaging of tissue samples. TPM provided molecular, cellular information
of tissues in the region of a few hundred microns on one side at a sub-cellular resolution, and ran at approximately 40
frames per second. OCT provided structural information in the tissue region larger than TPM images at a sub-tenth
micron resolution by using 0.1 numerical aperture. OCT had the field of view of 800 um × 800 um based on a 20x
objective, the sensitivity of 97dB, and the imaging speed of 0.8 volumes per second. This combined system was tested
with simple microsphere specimens, and then was applied to image the explanted intestine of a mouse model and the
plant leaves. Morphology and micro-structures of the intestine villi and immune cells within the villi were shown in the
intestine image, and chloroplasts and various microstructures of the maize leaves were visualized in 3D by the combined
system.
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