Detection of coagulating blood under steady flow by statistical analysis of backscattered signals

The main purpose of this study is to detect blood coagulation under flow condition by analyzing Nakagami statistical model of backscattered signals. The radiofrequency (RF) signals backscattered from flowing blood were measured with a 10-MHz focused transducer. A 30-ml aliquot of blood was circulated in the flow model, and 3 ml of 0.5 M calcium chloride solution was added to induce blood coagulation. The progression in the blood coagulation due to the addition of the calcium chloride solution resulted in the integrated backscatter being increased by 4.2 +/- 0.5 dB, then tended to stabilize as the clot was formed. The Nakagami parameter was approximately 0.75 +/- 0.1 for flowing blood during the initial stage of blood coagulation, and it increased rapidly to its highest level of 2.6 +/- 0.5 during clotting. These experimental results demonstrate the feasibility of using the ultrasonic statistical parameter for detecting blood coagulation from flowing blood and provide a novel method for further monitoring the progress of clotting and thrombosis in vivo.