A new ultrasound principle for characterizing erythrocyte aggregation: In vitro reproducibility and validation

RATIONALE AND OBJECTIVES. There is no method currently available to quantify erythrocyte aggregation in vivo. In this work, using a Couette system, we defined new ultrasound indexes potentially applicable for non-invasive investigations. METHODS. Two ultrasound protocols were developed: (1) a protocol in which decreasing shear rates ranging from 200 to 1 s^-1 were applied to solutions; and (2) a protocol in which a 200 s^-1 shear rate was initially applied followed by stoppage of flow (a kinetics protocol). New ultrasound indexes were defined as: the power P_US at the nominal frequency of each transducer, Rayleigh's slope (tangent of the curve P_US = f(log(F)) through the 3.5 to 15 MHz frequency bandwidth) and kinetic indexes characterizing the aggregation/aggregability of the suspension. RESULTS. Using washed erythrocytes resuspended in saline, it was shown that the ultrasound intensity is dependent at 3.54 ± 5.9% (NS) to the power of the frequency (theoretical value = 4). Using 10 total blood samples extracted from a single pig, good reproducibility for all indexes (5%) was demonstrated. CONCLUSIONS. A suitable and reproducible methodology was developed and validated for studying erythrocyte aggregation in calibrated in vitro conditions.