A homogeneous color of arterial flow can be obtained by increasing the scale. Flow toward the transducer typically appears red on color Doppler sonograms when a red color appears above the baseline on the color bar. Inversion can electronically invert the direction of flow, which may complicate the interpretation of the flow direction. Therefore, the flow direction should be interpreted based on the setting of the color bar. The wall filter WF eliminate the low frequency noise that may arise from vessel wall motion below an operator-defined frequency threshold [ 9 , 14 ].
WF settings are usually preset by manufacturer Fig. Bottom: On the Doppler spectrum, time seconds is represented on the x-axis. Flow direction relative to the transducer is shown in relation to the spectrum baseline arrow. The aliasing artifact on the Doppler spectrum can be adjusted by lowering the baseline arrowhead and increasing the scale. Note the spectral broadening arrow in the Doppler spectrum due to stenosis of the artery. SV, sample volume. It is important to understand the meaning of the parameters of pulsed-wave Doppler US and how to adjust them.
The sample volume cursor is composed of parallel lines on both sides of the arterial axis line. The sample volume should be placed within an arterial lumen, and the range of the sample volume size is generally from one-third to one-half of the luminal diameter [ 15 ].
On Doppler US, the line in the center of the artery indicates of the axis of arterial flow. The nearly vertical line is the Doppler line of sight Fig. The Doppler spectrum is a graph showing the mixture of frequencies over a short period of time [ 9 ]. The Doppler frequency is defined as the difference between the received and transmitted frequencies when blood cells are moving. The key elements of the Doppler spectrum are the time and velocity scales [ 9 ]. Flow direction relative to the transducer is shown in relation to the spectrum baseline.
Flow toward the transducer is represented by positive velocity above the baseline Fig. The RI is one of popular measurements of the pulsatility representing peripheral flow resistance [ 9 ]. If an aliasing artifact is present in the Doppler spectrum, the baseline can be reduced or the scale increased in order to optimize the velocity range Fig.
The Doppler waveform of the lower extremity arteries at rest is classified as a high pulsatility waveform and is characterized by a triphasic flow pattern [ 9 ]. Over the course of each heartbeat, a tall, narrow, and sharp systolic peak in the first phase is followed by early diastolic flow reversal in the second phase, and then by late diastolic forward flow in the third phase Fig.
Diastolic flow reversal results from the high peripheral resistance of normal extremity arteries [ 9 ]. In normal extremity arteries, flow acceleration in systole is rapid, which means that the peak velocity is reached within a few hundredths of a second after ventricular contraction begins. Blood in the center of the artery moves faster than blood at the periphery, which is described as laminar flow [ 9 ].
When the flow is laminar, the blood cells are moving at a similar speed. These features of normal arteries produce a clear space, known as the spectral window, under the Doppler spectrum. Doppler US of the lower extremities can be performed by obtaining grayscale images before the color Doppler study; however, grayscale evaluations are sometimes optional and can be considered as a second step when a color Doppler study yields findings suspicious for stenosis or occlusion.
On a grayscale image, the presence and the size of a plaque should be described, as well as whether the plaque is calcified or not. Plaque size can be measured in terms of height and length obtained using transverse and longitudinal scans, respectively [ 16 ]. Three-dimensional US has been recently used for measuring plaque volume, with good intraobserver and interobserver reproducibility [ 17 ].
On color Doppler US, if an occlusion is present in the artery, color flow is absent within the lumen Fig. Color flow is absent in the superficial femoral artery arrow on color Doppler sonogram at the inguinal level, representing complete occlusion. The red vessel is the deep femoral artery and the blue vessel is the collapsed femoral vein.
The Doppler spectrum at severely stenotic arterial segments and poststenotic or post-obstructive distal arterial segments is briefly reviewed below. The area of flow disturbance showing spectral broadening occurs within 2 cm beyond the area of stenosis due to loss of the laminar flow pattern Fig. The lower extremity artery waveform may convert to a low-resistance form with low pulsatility after exercise or as a result of the occlusion of more proximal arteries [ 18 ].
If the waveform is monophasic, that means that the entire waveform is either above or below the Doppler spectrum baseline, depending on the orientation of the US transducer [ 9 ]. However, if the operator is familiar with the US anatomy of the lower extremity arteries and understands the parameters and Doppler waveforms of Doppler US, accurate diagnostic results can be produced with less scanning time. No potential conflict of interest relevant to this article was reported.
National Center for Biotechnology Information , U. Journal List Ultrasonography v. Published online Jan Ji Young Hwang. Author information Article notes Copyright and License information Disclaimer. This article has been cited by other articles in PMC. Abstract Doppler ultrasonography of the lower extremity arteries is a valuable technique, although it is less frequently indicated for peripheral arterial disease than for deep vein thrombosis or varicose veins.
Introduction Imaging modalities for evaluating peripheral arterial disease in the lower extremities include computed tomography CT angiography, conventional angiography, and Doppler ultrasonography US. Anatomy of the Lower Extremity Arteries on CT Angiography Each lower extremity artery is visible with an accompanying vein, extending from the iliac artery to the popliteal artery.
Open in a separate window. The anatomy of the lower extremity arteries on computed tomography CT angiography. Normal color Doppler ultrasonography of the femoral arteries in the inguinal area. US Technique Transducer and Patient Position A linear transducer with a variable ultrasound frequency of MHz is generally used, but a convex transducer with a lower frequency can be selected for the evaluation of iliac arteries in the pelvic cavity [ 13 ].
Parameters and Optimization of Doppler US The operator should be aware of both color and pulsed-wave Doppler parameters and how to adjust these parameters to obtain an optimal Doppler image. Color and pulsed-wave Doppler sonograms of normal lower extremity arteries with parameters.
Adjustment of pulsed-wave Doppler ultrasonography in a stenotic arterial segment. Doppler Spectrum of Normal Lower Extremity Arteries The Doppler waveform of the lower extremity arteries at rest is classified as a high pulsatility waveform and is characterized by a triphasic flow pattern [ 9 ].
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Compare namely diff each case's output of test runners in different languages JavaScript and Java for now , and generate a report file. Source codes of velocity implementation in different programming languages, and all dependencies. Test cases, each of which has a.
Diffing the output results of test runners in different language versions, generating file result. Source codes of test runners in different language versions. Test runners run upon test cases as the input, and output into output folders of each language version. DOI: In Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography 22 1 , ; quiz In European journal of echocardiography : the journal of the Working Group on Echocardiography of the European Society of Cardiology 10 1 , pp.
In European heart journal 33 19 , pp. BSA, body surface area; LV, left ventricular. Lang, Roberto M. In European heart journal cardiovascular Imaging 16 3 , pp. Part 1: aortic and pulmonary regurgitation native valve disease. In European journal of echocardiography : the journal of the Working Group on Echocardiography of the European Society of Cardiology 11 3 , pp.
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