Optical clearing of flowing blood using dextrans with spectral domain optical coherence tomography

Abstract

Spectral domain optical coherence tomography (SDOCT) images have been used to investigate the mechanism of optical clearing in flowing blood using dextrans. The depth reflectivity profiles from SDOCT indicate that dextrans become increasingly more effective in reducing scattering in flowing blood, except for 5 mgdl(-1) of Dx500, with increasing molecular weights (MW 70,000 and 500,000) and concentrations (0.6, 2, and 5 mgdl(-1)). Among the tested dextrans, Dx500 at 2 mgdl(-1) had the most significant effect on light scattering reduction with the strongest capability to induce erythrocyte aggregation. Dx500 at 5 mgdl(-1) contributes more refractive index matching but induces a decrease in aggregation that leads to the same level as 0.6 mgdl(-1) Dx500. Previous studies identified various mechanisms of light scattering reduction in stationary blood induced by optical clearing agents. Our results suggest that erythrocyte aggregation is a more important mechanism for optical clearing in flowing blood using dextrans, providing a rational design basis for effective flowing blood optical clearing, which is essential for improving OCT imaging capability through flowing blood.

Figures

Fig. 1

Typical OCT images and corresponding 1D signal recorded from porcine blood (HCT=45%): (a) and (b) without dextran; (c) and (d) with 0.6% D×500; (e) and (f) with 2% D×500.

Fig. 2

Summary of attenuation in the blood at HCT=35%, 45%, and 55% without and with D×500 at a flow rate of 5 mm/sec (n=3).

Fig. 3

Attenuation reduction in the blood (HCT=45%) induced by D×70 and D×500 at concentrations of 0.6, 2, and 5 mgdl−1 (n=3).

Fig. 4

Attenuation reduction in blood (HCT=45%) induced by D×500 at flow rates of 5, 10, and 100 mm/s (n=3).

Fig. 5

Smear microscopy images for blood (HCT=45%) with D×70 and with D×500 at concentrations of 0.6, 2, and 5 mgdl−1 at a flow rate of 5 mm/sec. Dextran efficiency in inducing aggregation increases with MW. (Color online only)