Two-dimensional blood flow vectors obtained with bidirectional Doppler ultrasound.

Precise measurement of blood flow is important because blood flow closely correlates formation of thrombus and atherosclerotic plaque. Among clinically applied modalities for blood flow measurement, color Doppler ultrasound shows two-dimensional (2D) distribution of one-dimensional blood flow component along the ultrasound beam. In the present study, 2D blood flow vector is obtained with high temporal and bidirectional Doppler ultrasound technique. Linear array probe with the central frequency of 7.5 MHz and an ultrasound data acquisition system with 128 transmit and 128 receive channels were equipped. Frame rate of 5 kHz was achieved by parallel receive beam forming with a wide transmitted wave. The flow velocity was measured from two different angles by beam steering. The interval of two measurements was 0.8 msec and it was considered as almost one moment to obtain 2D blood flow vector. B-mode image and 2D blood flow vector of the pulsatile flow in a carotid artery model showed small vortex at the bifurcation area. The method was also applied for visualization of in vivo blood flow vector in human carotid arteries. 2D blood flow measurement may predict the risk area of thrombus and plaque formation induced by abnormal blood flow.

Validation of Echo-Dynamography by virtual color doppler echocardiography generated from phase contrast magnetic resonance angiography datasets.

Echo-Dynamography (EDG) is a smart visualization technique in echocardiography in which two-dimensional distribution of blood flow vectors in cardiovascular system is deduced by applying fluid dynamics theories into Doppler velocity datasets. Previous validation studies such as numerical simulation of free jet model or model circulation were too simple to reproduce unstable and asymmetrical flow in left ventricle. In the present study, virtual color Doppler echocardiography is generated from PC-MRA (phase contrast magnetic resonance angiography) datasets. EDG is applied on virtual Doppler data and the blood flow vectors are compared with those of the original PC-MRA data. EDG-derived blood flow vectors showed similar pattern as the original PC-MRA data when blood flow velocity had high value. The errors were caused from underestimating the magnitude of vortex flow component in the flow field near the boundary of the left ventricular wall. The results also indicated that apical long axis view had small error compared with parasternal long axis view. Despite EDG method causes small errors, it provides important information on blood flow dynamics in most parts.