The direct visualization of blood flow by real-time ultrasound: clinical observations and underlying mechanisms.

Abstract

The observation of spontaneous low-amplitude echoes from the blood in the larger blood vessels has not been satisfactorily explained. In vitro experiments were performed to study flowing and stationary blood by ultrasound. In both cases numerous low-level echoes were seen in blood and suspensions of washed red cells. No echoes were observed in plasma or solutions of hemoglobin. It was concluded that the red blood cells is the most likely scattering agent responsible for the contrast effect observed clinically.

Portal venous gas after hepatic transplantation: sonographic detection and clinical significance

“…The high-amplitude echoes were detected only in the portal vein and its branches and in one patient in the superior mesenteric vein, not in the hepatic veins or inferior vena cava, making it unlikely that these echoes were due to RBC aggregates or other particulate matter in the circulation. Experimentally, these air bubbles have been easily differentiated from the low-amplitude echoes reflected from moving ABCs [8]. The high-amplitude echoes from small particles easily seen at real time and the transient nature of this phenomenon are both typical sonographic findings of gas.…”

Sonographic diagnosis of gas embolism in the portal vein

“…Gas bubbles are characterized by large, high-amplitude echoes, sometimes with acoustic shadowing. These echoes can easily be differentiated from low-amplitude reflections, caused by blood cells, which may be detected even in the lumen of the portal vein of normal individuals [13].…”

Further Studies on Ultrasonic Backscatter from Blood

“…Several reasons may have contributed to this minor discrepency. ( 1 ) Curve fitting was achieved with a limited number of data points(8-12 points).…”