Lower limb artery Doppler
Doppler ultrasonography of the lower extremities is a valuable technique, although it is less frequently indicated for peripheral artery disease than deep vein thrombosis or varicose veins. Ultrasonography confirms stenosis by direct visualization of the plaque and analysis of Doppler waves in the stenotic and postostenotic arteries. To perform Doppler ultrasonography of the lower extremities, we need to know the anatomy of the lower extremities, the basic scanning techniques, and the parameters used in color and pulsed-wave Doppler ultrasonography.
Doppler US is a good method for screening and follow-up and for diagnosing peripheral artery disease.
Color Doppler US can be used to identify stenotic or overlapping sections.
The pulsed-wave Doppler US can show the exact flow velocity of each artery segment and determine the severity level of stenosis based on the pulsed-wave Doppler spectral waveform.
US anatomy of the lower extremities
Arteries can be distinguished from US veins by a number of features.
1. The arteries are rounded in inverted diagonals and the veins are somewhat oval.
2. The arteries are smaller than the veins.
3. Arteries have visible walls and sometimes calcified plaques on the walls.
4. When the vessels are constricted by the transducer, the arteries constrict partially, while the veins completely collapse.
The lower extremity Doppler begins at the US inguinal crease by placing the transducer on the common femoral artery in the transverse plane and placing the patient in a supine position.
The common femoral artery appears laterally to the femoral vein, which originates from the large saphenous vein in the inguinal region.
Below the inguinal crease, the superior femoral artery and the deep femoral artery are located along the femoral vein, a trans.....al scan showing a shape reminiscent of a Mickey Mouse face.
The common femoral artery, the divided superficial femoral artery, and the deep femoral artery are found in a dropped-Y configuration on a longitudinal scan.
Scanning is performed by moving the transducer along the medial femoral artery, away from the sartorius muscle, from the proximal to the distal femur. The superficial femoral artery runs along the femoral vein.
The popliteal artery is evaluated from the level of the knee crease in the transverse plane and is then approximated to the adductor canal at the supracondylar level of the femur.
The popliteal gastrocnemius muscle appears in the central part of the popliteal fossa between the medial and lateral heads. The posterior tibial artery can be evaluated proximally if it is scanned from its origin in the tibioperonial trunk, or from the medial malleolus posterior ankle.
The peroneal artery is scanned in the lateral part of the posterior calf and visualized with fibrous ****. Evaluation of the anterior tibial artery may begin from the anterior ankle to the thalamus neck and continue in close proximity, starting at the proximal anterolateral leg and continuing the distance between the tibia and fibula.
Continuing the first dorsal metatarsal artery between the first and second metatarsal bones, the transducer is located from the anterior ankle to the dorsal foot to assess the dorsal pedis artery.
Steps of color Doppler ultrasonography (US) for the lower extremities above the knee indicate the patient's condition. The red rectangular boxes are the scanning sites and planes needed for the femoral arteries and popliteal artery. The numbers in the boxes indicate the simple steps of scanning. The schema in the box displays the general US characteristics of the arteries and veins at each scanning site.
GSV, greater saphenous vein,
FV, femoral vein;
• common femoral artery;
• superficial femoral artery;
Deep femoral artery;
SSV, small saphenous vein;
POPV, popliteal vein;
popliteal artery.
American Technology
Transducer and patient position
A linear transducer with a variable ultrasound frequency of -15 9–15 MHz is commonly used, but a low-frequency convex transducer can be selected for evaluation of the iliac arteries in the pelvic cavity.
The transducer was placed on the artery for transverse scanning, and then rotated 90 for longitudinal scanning.
The artery should be scanned in the longitudinal plane for as long as possible.
The operator must rotate or move the transducer gently to maintain visualization of the artery. The pulsed-wave Doppler is displayed on a US longitudinal plane.
• The test usually puts the patient in a supine state. The patient's hip is usually abducted and rotated externally, and the knee is bent like a frog's leg so that the papillary artery in the papillary fossa and the posterior tibial artery in the medial calf can reach smoothly.
Left lateral decubitus position or prone position are options for evaluation of popliteal artery, posterior tibial artery and peroneal artery. The anterior tibial artery and dorsal pedis artery are scanned at the supine position.
Doppler US parameters and customization
The operator must know the color and pulsed-wave Doppler parameters and how to adjust these parameters to obtain the correct Doppler image. In these parameters
• Color box
• Color gain,
• Color Speed Scale,
Inverse
These parameters are often used during color Doppler US scanning.
Doppler spectrum of common lower extremity arteries
The Doppler wave of the lower extremities at rest is classified as a high pulsation wave and is characterized by a tripartite flow pattern.
During each heartbeat, there is a long, narrow and rapid systolic peak in the first stage, followed by a reversal of the initial diastolic flow in the second stage, and then a delayed diastolic forward flow in the third stage.
Diastolic flow reversal occurs as a result of high peripheral resistance of the common end arteries.
• In normal arteries, systole is the acceleration of flow, which means that the maximum velocity after the onset of ventricular contraction reaches a few hundredths of a second.
The blood in the center of the artery moves faster than the blood at the edge, which is described as laminar flow.
When the flow is laminar, the blood cells move at the same speed. These features of the normal arteries produce a clear spot under the Doppler spectrum, called the spectral window.
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