Characterization of blood properties from coagulating blood of different hematocrits using ultrasonic backscatter and attenuation

The influence of hematocrit on the change of blood properties during coagulating was extensively investigated using ultrasonic integrated backscatter and attenuation. Measurements were performed with porcine blood at hematocrits ranging from 25 to 55% using a 10 MHz transducer. Results showed that both integrated backscatter and attenuation are able to sensitively differentiate various stages of blood properties during coagulating. The slopes of integrated backscatter (S_r, dB/S) and attenuation (α _r, dB·cm^-1·MHz^-1·mS ^-1) are increased relative to hematocrit. The best fits for S _r and α_r as a function of hematocrit (H) equal to S_r = 0.0357 + 1.62e^-0.108H and α_r = 0.0281 + 0.003H, respectively. Variations of clotting time (T_s) and reaction time (T_α), estimated respectively from ultrasonic integrated backscatter and attenuation, associated with clot formation are also increased with hematocrit. This study demonstrates that blood hematocrit is a substantial factor affecting viscosity and backscattering properties of blood during coagulation capable of being discerned by ultrasonic backscattering and attenuation.