Items tagged “doppler”
10 results found
Article
Power Doppler
Power Doppler is a technique that uses the amplitude of Doppler signal to detect moving matter. Power Doppler:
is independent of velocity and direction of flow, so there is no possibility of signal aliasing
is independent of angle, allowing detection of smaller velocities than color Doppler, f...
Article
TIPS evaluation
TIPS evaluation is useful to ensure that a transjugular intrahepatic portosystemic shunt (TIPS) is working properly and that no stenosis has occurred within the stent. Ultrasound is often used as a first-line modality.
Radiographic features
Ultrasound
The normal TIPS should show color Doppler...
Article
Normal hepatic vein Doppler
The hepatic veins have a characteristic spectral Doppler waveform. Alterations in the normal hepatic vein waveform may reveal or confirm abnormalities in the heart or liver.
Terminology
The shape of the hepatic vein spectral Doppler waveform is primarily determined by pressure changes in the r...
Article
Wall filter
The wall filter in ultrasound is a way of filtering out low or high frequency Doppler signals. In clinical ultrasound, it is usually used to filter out very low frequencies that may add noise to a spectral Doppler waveform.
A typical use is removing the low frequency reverberation of an arteria...
Article
Transcranial Doppler sonography (ultrasound)
Transcranial Doppler (TCD), also known as transcranial color-coded duplex sonography (TCCS) is a sonographic study of intracranial structures and blood vessels, used most commonly to identify the hemodynamic state present in the vertebrobasilar circulation and the circle of Willis.
Termin...
Article
Spectral Doppler (ultrasound)
Utilizing automated Fourier analysis to convert returning sound waves into a series of individual frequencies, spectral Doppler refers to ultrasound modalities which yield graphical representations of flow velocity over time.
Terminology
The frequency of the sound waves returned to an ultraso...
Article
Tissue Doppler imaging (echocardiography)
A variant of pulsed wave Doppler, tissue Doppler imaging (TDI) is a modality in echocardiography that allows measurement of the velocity of myocardial movement throughout the cardiac cycle.
Physics
Color flow, pulsed wave, and continuous wave Doppler are designed to analyze the Doppler shifts ...
Article
Abnormal testicular Doppler flow (differential)
Abnormal testicular Doppler flow (arterial, venous, or both) can be a differential challenge. Always remember that the patient's presenting history helps quite a bit in narrowing the differential.
Reduced flow
partial testicular torsion (<360 degrees)
venous outflow is obstructed first, resul...
Article
Bernoulli equation (physics)
The Bernoulli equation utilizes the assumptions delineated in the law of conservation of energy to calculate a pressure gradient between two points from a velocity 1. In its simplified form, discussed below, it is often used to quantify severity of valvular derangements in echocardiography.
Phy...
Article
Coandă effect (physics)
The Coanda effect refers to the phenomenon by which a narrow jet of liquid (or air) passing through an orifice directly in sequence with a solid (especially convex) surface will deviate from its path and adhere to this curved surface, following its shape in parallel.
The mechanism is thought to...
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