Articles
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31 results found
Article
Doppler waveforms
Doppler waveforms refer to the morphology of pulsatile blood flow velocity tracings on spectral Doppler ultrasound. Waveforms differ by the vascular bed (peripheral, cerebrovascular, and visceral circulations) and the presence of disease.
Radiographic features
Ultrasound
Doppler
Most authori...
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
Peak systolic velocity (Doppler ultrasound)
Peak systolic velocity (PSV) is an index measured in spectral Doppler ultrasound. On a Doppler waveform, the peak systolic velocity corresponds to each tall “peak” in the spectrum window 1.
Explanation
When traveling with their greatest velocity in a vessel (i.e. during systole), red blood cel...
Article
Diastolic pseudogating
Diastolic pseudogating appears as periodic bright and dark signal in arteries such as the aorta as one progresses through a series of images. Synchronisation of the cardiac cycle and the pulse sequence results in high signal in the artery during diastole when blood is relatively stationary and l...
Article
LumiFlow
LumiFlow is a postprocessing technique for color or power Doppler ultrasound, which produces a relief-like visualization of the depicted vasculature.
Physics
Lumiflow can be applied to both color and power Doppler imaging. It applies a shading with an artifical light source to create a three-...
Article
CT pelvis (protocol)
The CT pelvis protocol serves as an outline for the acquisition of a pelvic CT. As a separate examination, it might be performed as a non-contrast or contrast study or might be combined with a CT hip or rarely with a CT cystogram. A pelvic CT might be also conducted as a part of other scans such...
Article
Spontaneous echocardiographic contrast (SEC)
Spontaneous echocardiographic contrast (SEC), also known as “echocardiographic smoke” is an echogenic swirling pattern of blood flow created by enhanced ultrasonic back-scatter from clumping of the cellular components of blood in instances of stagnating or low-velocity (low-flow states) 1. It di...
Article
Color flash artifact
The color flash artifact is a commonly encountered artifact on color Doppler ultrasound, representing spurious flow signal arising due to tissue/transducer motion.
Physics
The flash artifact is caused by movement of reflective tissues (e.g. due to respiration), or the transducer, which genera...
Article
Color-write priority
Color-write priority is an adjustable setting of color Doppler duplex ultrasound and determines whether a particular pixel on the image displays color or grayscale B-mode information at the moment.
Color-write priority is rarely changed directly during routine ultrasound imaging, even though it...
Article
Velocity encoding
Velocity encoding or Venc is referred to as an operator-controlled parameter for the determination of the maximum velocity within a velocity-encoded phase contrast imaging study.
Usage
Velocity-encoding (Venc) gradients are used to generate a phase shift in magnetic resonance phase contrast im...
Article
Reynolds number
The Reynolds number (Re) is the primary parameter used to define the transition of fluid motion between laminar and turbulent flow patterns 1. The Reynolds number represents the ratio of inertia forces to viscous forces, and as such has no units (i.e. is a dimensionless quantity) 1.
Calculatio...
Article
Doppler angle correction
Doppler angle correction refers to an imaging post-processing method used to adjust for the effects of insonation angle on the Doppler shift.
Technique
Measurement of flow velocity with Doppler imaging is dependent on the angle between the ultrasound beam and the target (insonation angle), wit...
Article
Blooming artifact (ultrasound)
Blooming or color bleed artifact occurs when the color signal indicating blood flow extends beyond its true boundaries, spreading into adjacent regions with no actual flow.
This artifact mainly affects the portion of the image distal to the vessel and the transducers. It is somewhat similar to ...
Article
MR vessel wall imaging
MR vessel wall imaging (VW-MRI) refers to MRI techniques used to evaluate for disease within the walls of arteries, beyond the luminal abnormalities depicted on angiographic imaging. This can be used anywhere in the body but is particularly important intracranially in distinguishing between vari...
Article
Contrast-enhanced MR angiography
Contrast-enhanced MR angiography (MRA) is a technique involving 3D spoiled gradient-echo (GE) sequences, with the administration of gadolinium-based contrast agents (GBCA). It can be used to assess vascular structures of almost any part of the body. Its key features are:
T1 weighted spoiled gra...
Article
End-diastolic velocity (Doppler ultrasound)
End-diastolic velocity (EDV) is an index measured in spectral Doppler ultrasound. On a Doppler waveform, the EDV corresponds to the point marked at the end of the cardiac cycle (just prior to the systolic peak) 1. In some equipment, the timing of cardiac cycle events may be automatically marked ...
Article
Abnormal ductus venosus waveforms
Abnormal ductus venosus waveforms can arise in a number of conditions ranging from aneuploidy to vascular malformations and fetal tumors. "A wave" reversal can be seen in 5% of euploid fetuses 9.
Pathology
Abnormal waveforms in fetal ductus venosus flow assessment can occur in a number of situ...
Article
Indocyanine green lymphangiography
Indocyanine green (ICG) lymphangiography is an emerging imaging technique used to visualize lymphatic vessels and map their course as they drain to sentinel lymph nodes.
History
Indocyanine green is a fluorescent dye discovered by researchers at Kodak working on near-infrared photography in 1...
Article
Nyquist limit
The Nyquist limit represents the maximum Doppler shift frequency that can be correctly measured without resulting in aliasing in color or pulsed wave ultrasound.
Physics
The Nyquist limit always equals Pulse Repetition Frequency (PRF)/2 3. The US machine can display the Nyquist limit either a...
Article
Electrical interference artifact (ultrasound)
Electrical interference artifact is an ultrasound artifact usually caused by the ultrasound machine being too close to the unshielded electrical equipment. The disturbance appears as arc-like moving bands in the ultrasound image.
While the presence of electrical equipment (e.g unshielded vent...
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