Estimation of hematocrit by means of attenuation measurement of ultrasonic wave in human blood

Precise determination of the attenuation of ultrasonic waves in blood is essential in the measurement of hematocrit. Laboratory setup records echoes scattered on blood cells, being measured simultaneously at different depths across the vessel diameter. After the echoes from two sample volumes positioned symmetrically to the center of the vessel were acquired, their quotient - proportional to the attenuation of ultrasound in blood was calculated. The aim of present work was the estimation of attenuation of ultrasound in different blood samples. The attenuation coefficient was determined in human blood at 37/spl deg/C by the pulse-echo technique. The experiments were done in 168 blood samples with hematocrit varying from 23.9 to 51.6 % and in 5 samples of plasma. The measurements were done at the frequencies 16 MHz and 20 MHz. The measured attenuation coefficient increased linearly with hematocrit (HCT). In the second part of work, the ultrasonic attenuation in blood was measured in vivo. The Doppler signal was recorded in the common carotid, brachial and radial arteries using 64-gate pulse Doppler flowmeter.