3. INTRODUCTION
Ultrasonography can diagnose stenosis through the direct
visualization of plaques and through the analysis of the Doppler
waveforms in stenotic and post stenotic arteries.
To perform Doppler ultrasonography of the lower extremity arteries,
the operator should be familiar with the arterial anatomy of the
lower extremities, basic scanning techniques, and the parameters
used in color and pulsed-wave Doppler ultrasonography
5. ULTRASOUND TECHNIQUE
5 MHz Linear Transducer(Range 3- 10 MHZ)
The transducer is placed over an artery for transverse scanning,
and then is rotated 90° for longitudinal scanning
The artery should be scanned on a longitudinal plane as long as
possible
Optimize Gray Scale And Color Doppler Parameters
Adjust Pulse Repetition Frequency(PRF) To Detect Hemodynamic
Disturbances
Perform Pulse Doppler In Regions Of Color Aliasing/distubance
8. ULTRASOUND ANATOMY OF THE LOWER
EXTREMITY ARTERIES
Arteries can be differentiated from veins on US by several
characteristics.
Arteries are round in transverse images, while veins are somewhat oval.
Arteries are smaller than veins.
Arteries have visible walls and sometimes have calcified plaques on the
walls.
When the vessels are compressed by the transducer, arteries are
partially compressed, while veins are completely collapsed
13. PERIPHERAL ARTERIAL DISEASE
Narrowing or blockage of the vessels that carry blood from heart to the
legs
RISK FACTORS
Diabetes
Smoking
Advancing age
Hypercholesterolemia
Hypertension
Obesity
15. Waveform shape
Peak systolic velocity
Spectral window
COMPONENTS TO LOOK FOR IN STENOSIS
16. 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.
Most authorities describe three types based on the number of phases of
flow in each cardiac cycle
17. TRIPHASIC FLOW
Doppler spectrum of normal lower extremity arteries
having three phases, due to crossing the zero flow baseline twice in
each cardiac cycle
systolic forward flow
early diastolic flow reversal (below zero velocity baseline)
late diastolic forward flow (slower than in systole)
21. PEAK SYSTOLIC VELOCITY
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.
23. PEAK SYSTOLIC VELOCITY
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.
24. SPECTRAL WINDOW
In normal straight vessels, blood flows are mostly in parallel and of
constant velocities. Thus, Doppler spectral wave-forms appear
concentrated and have no low velocity blood flow, thereby forming a so-
called spectral window due to the absence of Doppler signal below the
spectrum.
When blood flow velocity is non-parallel flow, a wide range of blood flow
velocities can be recorded simultaneously, resulting in spectral
broadening of Doppler spectral waveforms.
When low velocity turbulence arises in blood vessels, the turbulent
signals will appear in the original spectral window, causing a
disappearance or decrease in the spectral window, which is called
spectral fill-in
38. REPORT WRITING
Arteries of lower limbs shows normal tri-phasic flow
No atherosclerotic plaques are seen in major arteries of both lower limbs
The blood flow velocities are with in normal range in all major arteries
and their main branches in both lower limbs down to dorsalis pedis
arteries in feet
The arterial supply of the lower limbs originates from the external iliac artery. The common femoral artery is the direct continuation of the external iliac artery, beginning at the level of the inguinal ligament. The common femoral artery becomes the superficial femoral artery at the point where it gives off the profunda femoris.The popliteal artery is the direct continuation of the SFA in the adductor canal. The popliteal artery terminates into the anterior tibial artery and the tibioperoneal trunk. The anterior tibial artery passes through the interosseous membrane to reach the anterior compartment of the leg. It continues to the dorsum of the foot as the dorsalis pedis artery. The tibioperoneal trunk divides into the posterior tibial and peroneal arteries. The posterior tibial artery passes downwards and behind the medial malleolus.
It divides into medial and lateral plantar arteries. The peroneal (fibular artery) descends in the deep part of the posterior compartment, just medial to the fibula, supplying a perforating branch to the lateral and anterior compartments.
Transducer; A linear transducer
The operator should rotate or move the transducer delicately to maintain visualization of the artery. Pulsed-wave Doppler US is performed in the longitudinal plane
Patient position; The examination is usually performed with the patient placed in the supine position. The patient’s hip is generally abducted and externally rotated, and the knee is flexed like frog legs in order to easily approach the popliteal artery in the popliteal fossa and the posterior tibial artery in the medial calf
The anterior tibial artery and dorsalis pedis artery are scanned in the supine position
Arteries have visible walls
Having 3 layers
and sometimes have calcified plaques on the walls
Doppler US of the lower extremity begins at the inguinal crease by putting a transducer on the common femoral artery in the transverse plane with the patient in the supine position, showing a shape reminiscent of Mickey Mouse’s face on a transverse scan).
The common femoral artery, the bifurcated superficial femoral artery and deep femoral artery are seen in a fallen-Y configuration in a longitudinal scan
From the proximal to distal thigh, scanning is performed by moving a transducer distally in longitudinal plane along the superficial femoral artery deep to the sartorius muscle. The superficial femoral artery goes together with the femoral vein
The popliteal artery is evaluated from the knee crease level in the transverse plane which is seen in the central portion of popliteal fossa and divides into anterior tibial and tibioperonial trunk.
The evaluation of the posterior tibial artery can be started from its origins at the tibioperoneal trunk, if scanning distally.
The peroneal artery is scanned along the lateral side of the posterior calf and is visualized alongside the fibular bone
The evaluation of the anterior tibial artery can be started from the ankle anterior to the talus neck and continued.
The transducer is traced from the anterior ankle to the dorsal foot to evaluate the dorsalis pedis artery, continuing to the first dorsal metatarsal artery between the first and second metatarsal bones
Most common sites for atherosclerosis is at bifurcation
The Doppler waveform normal triphasic flow pattern . 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 .
Having two phases. The loss of third indicates a degree of disease
systolic forward flow
either of the following (controversial):
diastolic flow reversal without late diastolic forward flow (more common) - an indication of loss of elasticity of a vessel
zero diastolic flow reversal and pan diastolic forward flow (slower than in systole) - results from vasodilatation in response to compromised flow
having one phase indicating significant disease
No diastolic flow at all – indicates an approaching downstream significant stenosis occlusion
Almost vein like flow - slow systolic rise and slow diastolic fall – post severe stenotic disease
Spectral waveforms obtained from a normal proximal superficial femoral artery ( SFA ). The waveforms show a triphasic velocity pattern and contain a narrow band of frequencies with a clear area under the systolic peak. Peak systolic velocities are approximately 80 cm/s.
Normal Doppler spectrum with spectral window (indicated by arrow).
(B) Spectral broadening in non-parallelflow.
(C) Fill-in of spectral window by low-velocity flow and turbulence.
In normal straight vessels, blood flows are mostly in parallel and of constant velocities. Thus, Doppler spectral wave-forms appear concentrated and have no low velocity blood flow, thereby forming a so-called spectral window due to the absence of Doppler signal below the spectrum.
When blood flow velocity is non-parallel flow, a wide range of blood flow velocities can be recorded simultaneously, resulting in spectral broadening of Doppler spectral waveforms.
When low velocity turbulence arises in blood vessels, the turbulent signals will appear in the original spectral window, causing a disappearance or decrease in the spectral window, which is called spectral fill-in
Velocity ratio is determined by Peak systolic velocity at stenosis (PSV B) divided by Peak systolic velocity 2cm proximal to stenosis (PSV A)
Femoral artery lumen filled with hypoechoic thrombus or embolus
Good delineation of vessel wall without signs of plaque
Normal flow in adjacent FV
Grayscale longitudinal ultrasound image showing focal dilatation suggestive of aneurysm
Transverse and longitudinal gray scale ultrasound images
Intimal flap can be seen