Simultaneous assessment of red blood cell aggregation and oxygen saturation under pulsatile flow using high-frequency photoacoustics.

Tae-Hoon Bok,Eno Hysi,Michael C. Kolios

doi:10.1364/boe.7.002769

Abstract

We investigate the feasibility of photoacoustic (PA) imaging for assessing the correlation between red blood cell (RBC) aggregation and the oxygen saturation (sO2) in a simulated pulsatile blood flow system. For the 750 and 850 nm illuminations, the PA amplitude (PAA) increased and decreased as the mean blood flow velocity decreased and increased, respectively, at all beat rates (60, 120 and 180 bpm). The sO2 also cyclically varied, in phase with the PAA for all beat rates. However, the linear correlation between the sO2 and the PAA at 850 nm was stronger than that at 750 nm. These results suggest that the sO2 can be correlated with RBC aggregation induced by decreased mean shear rate in pulsatile flow, and that the correlation is dependent on the optical wavelength. The hemodynamic properties of blood flow assessed by PA imaging may be used to provide a new biomarker for simultaneous monitoring blood viscosity related to RBC aggregation, oxygen delivery related to the sO2 and their clinical correlation.

Highlights

Red blood cells (RBCs) are mainly involved in the transport and exchange of physiologically relevant gasses
The PA amplitude (PAA) and the mean BFV (mBFV) were measured by high-frequency PA imaging at 750 and 850 nm and the Doppler velocity, respectively under pulsatile blood flow
The PAA varied periodically out of phase with the mBFV at all beat rate demonstrating the effect of aggregate size on the PAA

Summary

Introduction

Red blood cells (RBCs) are mainly involved in the transport and exchange of physiologically relevant gasses. The transport of oxygen is governed by the blood oxygen saturation (sO2) [1], a measure of the RBC’s oxygen carrying capacity. The sO2 measurement methods have been significantly improved through advances in photoacoustic (PA) imaging [7,8,9,10]. These previous studies have focused on the sO2 measurement by PA imaging in micron-diameter vessels without considering hemodynamic and/or hemorheological effects such as RBC aggregation

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