Observation of blood echogenicity variation in rat arteries using high-frequency ultrasound

Previous studies have demonstrated that blood echogenicity is highly variable depending on blood flow velocity and pulsatility mainly due to the variation of red blood cell (RBC) aggregation. However, most of the studies were performed in a mock-flow loop using porcine blood and the results were not fully validated in vivo. Rat was rarely used for investigation of RBC aggregation due to its low aggregation tendency. But high-frequency ultrasound may detect the RBC aggregation from rat blood. The purpose of the present study is to investigate the cyclic and radial variation of blood echogenicty in rat arteries using a high-frequency ultrasound system with a 40-MHz scanner. B-mode images of blood were acquired from various arteries, including carotid artery and abdominal aorta. Blood echogenicity increased at systole and decreased at diastole. The cyclic variation was larger at the vessel center than near the vessel wall. The central hypoechoic zone ('black hole' phenomenon) was observed in carotid arteries. The experimental results from rat arteries in vivo corroborate the previous observations of cyclic and radial variations of blood echogenicity from porcine blood in mock-flow loops. Acknowledgments: This work was supported by the Korea Research Foundation Grant funded by the Korean Government (NRF-2011-0017984).