Theoretical model for optical oximetry at the capillary level: exploring hemoglobin oxygen saturation through backscattering of single red blood cells

Rongrong Liu; Graham Spicer; Siyu Chen; Hao F. Zhang; Ji Yi; Vadim Backman

doi:10.1117/1.JBO.22.2.025002

3 February 2017 Theoretical model for optical oximetry at the capillary level: exploring hemoglobin oxygen saturation through backscattering of single red blood cells

Rongrong Liu, Graham Spicer, Siyu Chen, Hao F. Zhang, Ji Yi, Vadim Backman

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Journal of Biomedical Optics, Vol. 22, Issue 2, 025002 (February 2017). https://doi.org/10.1117/1.JBO.22.2.025002

Abstract

Oxygen saturation (sO2) of red blood cells (RBCs) in capillaries can indirectly assess local tissue oxygenation and metabolic function. For example, the altered retinal oxygenation in diabetic retinopathy and local hypoxia during tumor development in cancer are reflected by abnormal sO2 of local capillary networks. However, it is far from clear whether accurate label-free optical oximetry (i.e., measuring hemoglobin sO2) is feasible from dispersed RBCs at the single capillary level. The sO2-dependent hemoglobin absorption contrast present in optical scattering signal is complicated by geometry-dependent scattering from RBCs. We present a numerical study of backscattering spectra from single RBCs based on the first-order Born approximation, considering practical factors: RBC orientations, size variation, and deformations. We show that the oscillatory spectral behavior of RBC geometries is smoothed by variations in cell size and orientation, resulting in clear sO2-dependent spectral contrast. In addition, this spectral contrast persists with different mean cellular hemoglobin content and different deformations of RBCs. This study shows for the first time the feasibility of, and provides a theoretical model for, label-free optical oximetry at the single capillary level using backscattering-based imaging modalities, challenging the popular view that such measurements are impossible at the single capillary level.

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Rongrong Liu, Graham Spicer, Siyu Chen, Hao F. Zhang, Ji Yi, and Vadim Backman "Theoretical model for optical oximetry at the capillary level: exploring hemoglobin oxygen saturation through backscattering of single red blood cells," Journal of Biomedical Optics 22(2), 025002 (3 February 2017). https://doi.org/10.1117/1.JBO.22.2.025002

Received: 25 August 2016; Accepted: 9 January 2017; Published: 3 February 2017

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