Preliminary photoacoustic imaging of the human radial artery for simultaneous assessment of red blood cell aggregation and oxygen saturation in vivo

The main role of red blood cell (RBC) is oxygen delivery to body tissues via blood flow. When flowing blood is exposed to stasis or low shear rate (the radial gradient of velocity profile) in blood vessels, RBCs become aggregated resulting in alterations of blood viscosity affecting blood flow dynamics. Our group demonstrated that lower shear rate yielded greater aggregation and a higher PA signal while higher shear rates led to disaggregation thereby decreasing the PA signal amplitude (Bok et al., Biomed. Opt. Express, 2016). In this way, the relation between oxygen saturation (sO
₂
) and RBC aggregation may provide a new biomarker in diagnosis of blood flow. In this paper, we present a pilot study where high-frequency photoacoustic imaging (PAI) is used to for the simultaneous assessment of RBC aggregation and sO
₂
in vivo from the human radial artery (RA).