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Absence of the portal system in a first trimester case associated with hygroma and aorto-umbilical fistula. (A): Transverse plane of the upper abdomen with color Doppler applied, showing umbilical cord insertion, stomach, the prominent hepatic artery and no afferent liver venous perfusion; (B): midsagittal plane reconstructed from a three-dimensional volume acquisition were the crown-rump ...
Carotid ultrasound is dependent on operator skill, and other noted areas of limitation are poor insonation angle, poor blood flow, and deep artery location. [2] CEUS is prone to overinterpretation of vessel wall abnormalities, known as pseudoenhancement. [1]
Functional transcranial Doppler sonography (fTCD) is a neuroimaging tool for measuring cerebral blood flow velocity changes due to neural activation during cognitive tasks. [8] Functional TCD uses pulse-wave Doppler technology to record blood flow velocities in the anterior, middle, and posterior cerebral arteries.
Unlike 1D Doppler imaging, which can only provide one-dimensional velocity and has dependency on the beam to flow angle, [4] 2D velocity estimation using Doppler ultrasound is able to generate velocity vectors with axial and lateral velocity components. 2D velocity is useful even if complex flow conditions such as stenosis and bifurcation exist ...
Various techniques for calculating the direction of arrival, such as angle of arrival (AoA), time difference of arrival (TDOA), frequency difference of arrival , or other similar associated techniques. Limitations on the accuracy of estimation of direction of arrival signals in digital antenna arrays are associated with jitter ADC and DAC. [3]
In computer graphics and geography, the angle of incidence is also known as the illumination angle of a surface with a light source, such as the Earth's surface and the Sun. [1] It can also be equivalently described as the angle between the tangent plane of the surface and another plane at right angles to the light rays. [ 2 ]
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Doppler spectrum. Deliberately no units given (but could be dBu and MHz for example). This is an issue only with a particular type of system; the pulse-Doppler radar, which uses the Doppler effect to resolve velocity from the apparent change in frequency caused by targets that have net radial velocities compared to the radar device. Examination ...