Pulsatile changes of blood echogenicity in rat arteries using a high-frequency ultrasound system

Blood echogenicity is highly susceptible to hemodynamic conditions mainly due to the variation of erythrocyte aggregation. The purpose of the present study is to investigate the echogenicity variation in arterial blood flow to better understand hemodynamics and erythrocyte aggregation in in vivo rat arteries. Blood echogenicity in the carotid artery and the abdominal aorta of rats was measured using a high-frequency ultrasound imaging system with a 40 MHz probe. The ECG-based kilohertz visualization reconstruction technique was employed to obtain high temporal and spatial resolution images. Experimental results show that blood echogenicity increased at systole and decreased at diastole. Complex changes in the distribution of blood echogenicity, such as the 'black hole' or the 'bright collapsing ring' phenomena, were observed in some rats treated with dextran 500 or skin incision. The present in vivo study using rats and a high-frequency ultrasound imaging system corroborates the previous observations of cyclic and radial variations of blood echogenicity in in vitro studies.