Simultaneous photoacoustic detection of red blood cell aggregation and oxygenation

Red blood cell (RBC) aggregation is a reversible process which occurs in the presence of increased plasma fibrinogen concentration and low flow conditions. It results in the RBCs forming structures that resemble “stacks of coins” and/or clusters impairing blood flow and the ability of oxygen to diffuse to surrounding tissues. We investigate the use of photoacoustics (PA) to detect and monitor RBC aggregation and the effect of aggregation on the sample oxygenation level. In this study, porcine RBCs were illuminated at 750nm and 1064 nm and the oxygen saturation of each sample was estimated. Aggregation was induced by varying the concentration of Dextran-70. Changes in the photoacoustic signal strength suggest that in the presence of RBC aggregates, the release of oxygen into the surroundings is impaired. A 30% increase in oxygen saturation was measured based on changes in the PA signal when comparing the nonaggregated and aggregated blood samples. This work demonstrates that PA imaging has the potential to detect changes due to RBC aggregation and monitor oxygenation level.