A pulsed photoacoustic technique for studying red blood cell sedimentation

This study shows the capability of a pulsed photoacoustic (PA) technique to measure red blood cell sedimentation and aggregation processes in vitro. Red blood cells are the main source of absorption in blood. The PA signal is proportional to the sample’s optical absorption coefficient, and hence, dynamic changes in the sample can be monitored by analyzing the PA pulse amplitude and pulse arrival time. Optical coherence tomography (OCT) is used as a parallel method for comparison. Diluted whole blood and different concentrations of washed red blood cells were used as samples. The pulsed PA technique is suitable for monitoring changes in sedimentation velocity when dextran is added to the sample. When the measurement section with the fastest sedimentation rate was selected for analysis, a more than 10-fold increase in the sedimentation rate, induced by dextran, was found with both the PA and OCT techniques. The PA pulse delay was found to be a more reliable measure of changes in the sample than the PA signal amplitude.