Detecting the process of blood coagulation and clot formation with high frequency ultrasound

High frequency ultrasounds, up to 50 MHz, were applied to assess changes of blood properties during coagulating and clotting. Experiments were performed using calcium chloride solution to induce the blood coagulation (BC) and clot formation (CF) in porcine whole blood of various hematocrits ranged from 25 to 55%. The ultrasonic signals backscattered from the whole blood were digitized at a 500 MHz sampling frequency and collected for 30 minutes at one A-line per second temporal resolution. The corresponding M-mode images and integrated backscatters acquired from four transducers of different frequencies were processed to characterize blood properties. Two parameters, denoted as S _r and t_c respectively in response to the rate of change and duration between the onset of blood coagulation and the end of clot formation, were derived from the integrated backscatter as a function of time to further evaluate the sensitivity and accuracy for measurements. Results showed that backscattered signals acquired from different frequencies and their relative analysis may be applied to effectively detect the process of BC and CF. In particular, measurements using high frequency ultrasound tended to exhibits a better sensitivity to detect the coagulation, with larger average S _r and shorter t_c. respectively corresponding to 0.23 dB/sec and 756 seconds measured from a hematocrit of 35% using a 50 MHz transducer. The discrepancy between results of t_c measured by different frequencies may be readily associated with the resultant size of the resolution cell of the transducer and the pulse duration. Both ultrasonic M-mode image and integrated backscatter in this study were validated to monitor the process of BC and CF and specifically with those quantitative parameters, S _r and t_c. It enables a potential to further apply high frequency ultrasounds for early detecting BC and CF in clinical diagnoses.