Doppler of Lower Limb Arteries – Technical Aspects

Edited on 2016 August 10.

Dr WALIF CHBEIR

No financial relationships with commercial entities to disclose.

* General Rules:

1-Explain the procedure to the patient and answer any questions.

2-Obtain and document applicable patient history, signs and symptoms as well as risk factors on appropriate forms.

3-Verify that the procedure requested correlates with patient’s symptoms.

4- pertinent medical history: • Determine if the patient has a history of recent deep vein thrombosis (ankle-brachial indices would not be performed in the presence of deep vein thrombosis). • Ascertain whether the patient is taking vasodilator medications because they may influence the observed peripheral arterial waveforms (rendering them low-resistance biphasic, whereas they are normally high-resistance biphasic/triphasic). • Ascertain whether there is a relevant cardiac history such as heart failure (which reduces flow velocity) or aortic valve stenosis or insufficiency (which alters waveforms).

5- Perform a limited physical examination of the limbs in question.

6- Review any previous duplex studies available.

7- Select appropriate test settings, select appropriate annotation throughout test and record images during examination.

8-The patient lies supine for at least 10 minutes before scanning to avoid residual hemodynamic effects of exercise or muscular exertion.

9-Gloves are worn by the sonographer where there is a threat of contamination by infected body fluids.

10-Ensure that both limbs are scanned.

11- Using grayscale imaging and color Doppler flow mapping, identify all vessels in both their transverse and longitudinal planes and record flow velocities with pulsed-wave Doppler.

12- Perform spectral Doppler using: An angle of less than or equal to 60 degrees to the vessel wall where possible and a sample volume of 1.5mm.

* Real-Time Gray-Scale Imaging

– The diameter of the peripheral arteries that is clinically relevant varies from 1 to 6 mm. Accurate visualization of the arterial wall requires high-resolution transducers, more than 5 MHz, to visualize all the various lesions.

– A broad frequency range of 5 to 10 MHz is preferred because it offers overall good resolution while permitting good depth penetration, even in the thigh.

– For detailed visualization of smaller-diameter arteries, higher frequencies of 7 to 12 MHz can be used. At these high frequencies, transducers have poor depth penetration but may be useful for evaluating bypass grafts and the ulnar and radial arteries and smaller arteries of the hand.

– The linear phased array transducer is ideal for imaging the extremity arteries. The transducer has sufficient length to permit rapid coverage of long arterial segments by holding it parallel to the artery or graft long axis and by sliding it in a series of nonoverlapping increments.

– A smaller-footprint, curved array or sector transducer can be useful for imaging the iliac arteries.

– Gray-scale settings are adjusted to optimize visualization of intraluminal plaque or thrombus at these sites of abnormal flow.

* Doppler Sonography

Simultaneous display of Doppler spectral waveforms and data and the gray-scale image, duplex Doppler sonography, is the basic requisite for the evaluation of the peripheral arteries and arterial bypass grafts.

Careful real-time control is needed to position the Doppler sample gate and accurately detect sites of maximal blood flow velocity in arteries and bypass grafts. The transducer (doppler) carrier frequencies can vary between 3 to 10 MHz, tending to be best lower than the simultaneously acquired gray-scale image. Selection of a Doppler transducer frequency of approximately 5 MHz sacrifices some sensitivity for detecting slowly moving blood but decreases the likelihood that the system will alias at sites of rapidly moving blood, such as stenoses or arteriovenous fistulas.

The ultrasound beam is directed perpendicular to the surface of interest to obtain the brightest echo with gray-scale imaging and optimal imaging of the artery wall. The perpendicular angle is often readily obtained, as arteries generally are parallel to the surface of the transducer.

Vessel of interest should be perpendicular to ultrasound beam for B-mode imaging to obtain most distinct echoes. Left, Carotid B-mode image obtained with ultrasound beam perpendicular to vessel wall (arrow) demonstrates trilaminar structure of arterial wall. Right, Wall structure is poorly defined with nonperpendicular angle.

For the Doppler component of duplex imaging, an angle of 60 degrees between the Doppler insonation beam and the vessel wall should be maintained. This Doppler angle becomes an important consideration when the velocity data are used to classify disease. Angles above 60 degrees can result in significant overestimation of the velocity and should be avoided. Angles that are not relevant to the vessel wall may misrepresent the true peak velocity.

Angle of 60 degrees of Doppler insonation relative to vessel axis provides most accurate Doppler velocities. Angle correction should be used to maintain Doppler angle of 60 degrees or less. Doppler cursor should be parallel to vessel axis in center stream of arterial flow.

* Color Doppler sonography is an essential component of a peripheral arterial sonographic examination. The simultaneous display of moving blood superimposed on a gray-scale image allows a rapid survey of the flow patterns within long sections of the peripheral arteries and bypass grafts. In general, an efficient approach to peripheral vascular sonography relies on color flow Doppler sonography to rapidly identify zones of flow disturbances, then on duplex sonography, including Doppler spectral analysis, to characterize the type of flow abnormality present. The color Doppler image displays only the mean frequency shift caused by moving structures. The pixel size (resolution) is also coarser than the corresponding pixel size of gray-scale image. This may cause some ambiguity in alignment of the two separate images and can cause the color Doppler information to overlap beyond the wall of the arteries. Most manufacturers use lower transducer frequencies for the color flow image than for the gray-scale sonographic component of the image. This approach increases the depth penetration of the color flow image without compromising image resolution.

Color Doppler provides additional information used to detect a significant stenosis.

The pulse repetition frequency scale determines the degree of color saturation and is adjusted so that normal laminar flow appears as a region of homogeneous color.

Stenosis results in the production of a high velocity jet and an abrupt change in the color flow pattern. This is identified as either aliasing or desaturation (whitening) of the color display at the site of luminal narrowing. Aliasing occurs when the flow velocity exceeds the Nyquist limit and results in color display of the reverse flow direction (wrap around).

Color persistence is a continuous flow signal that is color of the forward direction only, in contrast to the alternating color in normal arteries. Color persistence corresponds to the monophasic spectral Doppler waveform of severe stenosis.

A color bruit in the surrounding soft tissue also indicates flow disturbance. This color artifact is attributed to vibration in the surrounding soft tissue in the presence of a high velocity jet.

The poststenotic region demonstrates a mosaic pattern indicating turbulent flow.

Abnormalities of color flow indicate possible stenosis that is then characterized using pulsed wave Doppler determination of velocities.

Color Doppler image obtained at carotid bifurcation. Laminar flow in external carotid artery is demonstrated

by homogenous color with lightest color toward center of vessel. Aliasing is evident at origin of internal

carotid artery (ICA) by abrupt color change from red to blue midstream at origin of ICA where large echolucent

plaque is present. Mosaic of color filling remainder of ICA is consistent with poststenotic turbulence.

* Power Doppler sonography is a variant of color flow Doppler imaging that displays a summation of the Doppler signals caused by moving blood. Advantages of power Doppler over color Doppler flow imaging are (1) the blood flow information does not alias, (2) the signal strengths are much less angle dependent, and (3) slowly moving blood is more easily detected. A disadvantage is the loss of information pertaining to the direction of blood flow, although this information can also be displayed.

Sensitivity is increased by a factor of 3 to 5 times with power Doppler compared with color flow Doppler. Power Doppler can, therefore, identify very slow flow that may not be detected by color flow Doppler. and it improves delineation of the lumen.

Power Doppler is used to differentiate high-grade stenosis from occlusion, to detect collateral vessels, and to identify small vessel disease.

* The advent of ultrasound contrast agent, as for the power Doppler, has extended the role of the Ultrasound in the evaluation of vascular involvement. In the proximal Lower Limb & iliac Vessels, the location of the vessels and confirmation of occluded segments has been made easier and, in the distal part of the leg, they make assessment of smaller vessels of calf & foot easier. However, more works is required to evaluate further their role.

* Duplex Doppler sonography with gray-scale and Doppler spectral analysis is well accepted as the primary noninvasive modality for detecting evidence of lower extremity bypass graft dysfunction. It can also be used to evaluate the success of peripheral angioplasty, atherectomy, and stent placement.

Doppler imaging of the leg arteries to determine the extent and nature of arterial lesions has become practical with the aid of color Doppler flow imaging. Although duplex Doppler sonography can be used to determine the presence of significant arterial lesions, the task of evaluating the whole leg is labor and time intensive. It takes 30 to 60 minutes to map out the arterial tree of each leg using Duplex ultrasound. With color Doppler mapping, this task can be accomplished in 15 to 20 minutes. Color Doppler imaging also improves the accuracy of Doppler ultrasound as a diagnostic test for detecting and grading the severity of peripheral artery disease.

A full scan of the lower limb arteries can be time consuming: In some case, a full scan (from Aortic Bifurcation to ankle or foot) is required but in other cases, the examination can be tailored to specific levels depending on the diagnostic information required. It is therefore useful if the diagnostic question can be clearly defined, so that the most appropriate examination can be performed.

Since quantification of stenoses is based on velocities and velocity increases, scanning of the arteries is undertaken longitudinally.

Atherosclerotic changes produce inconsistent effects in the B-mode image. Because of this, the colour image is used extensively to identify the location of the artery, voids in the flow signal indicating occlusion and regions of increased velocity suggesting narrowing of the lumen. Areas of concern can then be tested using spectral Doppler. For linear arrays, beam steering can enhance the Doppler image in both colour and spectral modes, although attenuation is least when the Doppler beam is unsteered.

Although limited, real-time gray-scale sonography is useful for evaluating the presence of atherosclerotic plaque or confirming the presence of extravascular masses.

The degree of stenosis is obtained by measuring peak systolic velocity from the spectral Doppler sonogram. As usual when using spectral Doppler ultrasound to calculate velocities, care should be taken when using beam/flow angles greater than 60°, although the use of velocity ratios means that errors are usually acceptable at angles up to 70°.

When determining occlusion, low pulse repetition frequencies and power Doppler should be used to check for low volume, low velocity flow in any residual lumen in the vessel.

Flow waveforms in healthy arteries exhibit pulsatile flow with reverse flow in late systole – triphasic or biphasic flow.

Normal Arterial Waveforms of CFA, Pop A and TPA.

Changes in flow waveform shape can be an indication of proximal disease or distal occlusion. Although attempts have been made to use measurement of subtle changes to indicate proximal disease, these have not become established in clinical practice. However, experienced sonographers use visual changes in the waveforms and abnormally low or high velocities as indications of abnormal circulation warranting further investigation.

Monophasic Waveform in a CFA. The loss of the reverse flow component and forward flow throughout diastole are indicative of proximal disease.

Abnormal superficial femoral artery flow waveform. The low velocities, absent diastolic flow and short initial peak are indicative of severe distal disease, in this case an occlusion of the femoral artery at mid-thigh level.

* During the scan:

Attempt to characterize the pathology (e.g., wall thickening/calcification [medial calcinosis]) and the appearance, length, location and extent of plaque.

If aneurysmal dilation is identified in transverse scanning, measure the diameter, length, and the aneurysmal neck, as well as any endovascular treatment relevant details (see Chapter 7).

Obtain representative peak systolic velocity (PSV) measurements along the vessels every 2 to 3 cm.

When a lesion is detected with grayscale scanning and color Doppler flow mapping, record PSV measurements: Immediately proximal to the site of stenosis, within the stenosis and immediately distal to it.

Note any obvious collateral vessel formation associated with a significant lesion.

Document any identified retrograde flow.

* Main Steps of the examination of the Lower Limb Arteries

1- Patient Supine: Scan CFA, proximal PFA and SFA down the adductor canal.

2- Patient (IpsiLateral) Decubitus: Scan adductor canal, Pop.A. to bifurcation and TPT, scan PTA and Per.A.

3- Patient Supine: Scan ATA. Scan Iliac arteries and Infrarenal aorta.

* Scanning Technique : Common Femoral, Profonda Femoris and Superficial Femoral Arteries:

The examination begins with the patient lying supine on the couch, limb being scanned is externally rotated and the knee slightly bent.

A high frequency linear array transducer, usually 5-12 Mhz, should be used; depending of the built of patient and the performance of the ultrasound system. However, Lower Frequencies curvilinear arrays may be required to examine the arteries in the adductor canal or in large patient, especially as it produces a greater field of view.

The Distal external Iliac / Common femoral artery is located using colour Doppler as it leaves the pelvis under inguinal ligament, at the level of the groin, lateral to the Common femoral vein. Imaging should be performed in the longitudinal plane, and a spectral Doppler should be obtained from this artery, even if flow appears normal on colour Doppler and there is no evidence of local disease, as change in this may indicate the presence of significant disease proximally, necessitating a careful direct examination of the iliac vessels.

The FCA should be followed distally to its bifurcation into the profunda femoris and superficial femoral arteries using colour Doppler and Doppler signals obtained from the origin of both the superficial femoral artery and the deep femoral artery.

The profunda femoris artery dives deeply beyond its origin and should be examined over its proximal 5cm, especially in patients with severe superficial femoral disease, in order to assess the amount of collateral flow or its potential value as a graft origin or insertion point.

The SFA is then followed distally as it courses down the medial aspect of the thigh using color Doppler. It’s often better to move the transducer in sequential steps, rather than sliding it down the tighs as most machines require a few frames of sampling at each position to provide a steady Image. In addition, the moving transducer generates color Doppler noise over the image, obscuring vascular details.

Doppler Spectra are obtained as necessary at points and areas of questionable disease and narrowing. Even if there no abnormalities in colour Doppler, it is good practice to obtain routine spectral assessment in the upper, middle and lower thigh, in order to confirm that there is no alteration in the waveform that suggests disease.

Sometimes, the artery is difficult to see on both B-mode and colour or power Doppler because of calcification and weakness or absence of signal, especially at depth and in patients

with diabetes or chronic renal failure. In these cases the artery can be visible by vitue of calcified plaques in the wall of vessel. Alternatively, the Femoral Superficial Vein, lying behind can be used as a guide to the position of the artery and spectral Doppler used to demonstrate the absence or presence of arterial flow. Echo-Contrasting Agents can be used if there is any continuing uncertainty concerning the patency of the artery.

There are 3 indirect signs of significant disease wich might be apparent during the examination and wich should prompt a careful review if a cause for these changes has not been identified :

1- Color Doppler may show the presence of collateral vessels in the muscles of the thigh.

(A) Collateral vessels in the muscles of the thigh. (B) A larger Collateral Vessel joining the lower superficial femoral artery.

2- Collateral Vessels may be seen leaving or joining the main artery.

3- The character of the specral waveform may show a change between 2 levels indicating a segment of disease somewhere between these 2 points.

* Scanning Technique : The adductor Canal and popliteal fossa

The patient is then turned into a lateral decubitus position so that the medial aspect of the leg being examined is uppermost as the distal portion of the superficial femoral artery may be easier

to evaluate from the distal posterior thigh as well as the popliteal artery in the popliteal region. It’s even better than the prone position as it allows to access in continuity to the lower superficial femoral artery, in the adductor canal area, the popliteal region and the medial calf.

The region of the adductor canal must be examined with a great care as it is a site where a short segment stenosis or occlusion may be present, and this section of the vessel can be difficult to visualise as it passes deep to the thigh muscles. In some cases the use of a lower scanning frequency may help visualisation. The SFA is examined as far down as it can be followed on the medial aspect of the thigh; The popliteal artery (Pop.A) is then located in the popliteal fossea and followed superiorly.

In difficult cases, a mark can be put on the skin of the medial thigh to show the lowest segment of SFA seen in Supine position; the Pop.A is then followed superiorly in the decubitus position until the transducer reaches the level of the skin mark, ensuring that the vessel has been examined in continuity. If concern persists about disease in this segment, spectral Doppler waveforms from the lower superficial femoral artery and upper popliteal artery segments should be obtained to ensure that there are no changes that might suggest significant intervening disease.

The Pop.A is then followed through the popliteal fossa, lying deep to the vein, and followed down to the point of division into the tibioperoneal trunk (TPT) and anterior tibial artery (ATA). Following the distal popliteal artery in a longitudinal plane, the origin of the anterior tibial artery can usually be visualized diving deep on the monitor. The anterior tibial artery can only be followed for a short distance from this approach. A Doppler spectral waveform should be recorded in the upper and inferior half of this Pop.A.

Scan Plane of the distal SFA as it passes through the adductor canal.

Courtesy of http://www.ultrasoundpaedia.com/normal-leg-arteries/

* Scanning Technique : Calf Arteries

The complexity of the assessment of the calf arteries depend of the clinical situation and local skills as well as type of radio – surgical team approach.

In general, the TPT and its bifurcation, Proximal ATA from posterior approach , the dorsalis pedis artery midway between lateral and medial malleoli and the posterior tibial artery at the ankle level immediately posterior to the medial malleolus are assessed by colour and spectral Doppler. If neither the posterior tibial nor the dorsalis pedis arteries are visualized, the peroneal artery is to search anterior or posterior to the lateral malleolus.

If the examination is to exclude proximal disease that would benefit from angioplasty or bypass grafts, then it is usually sufficient to assess the three calf arteries at the upper and mid- calf level, recording whether they are patent or not, in order to provide some assessment of the state of the distal run off.

In other cases, a more detailed examination is required to clarify changes seen in CTA or Arteriography or if a distal insertion point for distal graft is been thought. The increased sensivity of power Doppler is useful to detect weak signals from small or diseased but patent Vessels. Patency of the distal anterior tibial, posterior tibial and peroneal arteries is identified. Arteries are described in terms of diameter, patent length with evidence of stenoses, waveform shape and evidence of communication with the pedal arch. There have been fewer studies reporting on ultrasound scanning of infrapopliteal arteries. In comparison with scanning the

proximal arteries, investigation of vessels in the lower leg is time-consuming with a lower reported success rate, especially for peroneal artery stenosis. (48,49 in 3). The presence of extensive, severe calcification can preclude full investigation of calf arteries; this is a practical constraint on the many patients presenting with diabetes or chronic renal failure.

Calcification in the tibial arteries. Calcification in the tibial arteries causes loss of colour flow deep to high levels of calcification. In severe cases flow may not be detected by colour or spectral Doppler.

Nevertheless, a study comparing angiography and duplex scanning assessment of vessel patency (48 in 3) concluded that agreement between the two modalities was similar to agreement between radiologists reporting on angiograms. For these arteries, colour flow is particularly useful for identifying the course of vessels and the presence of collateral flow.

Ultrasound has been shown to be effective in evaluating run-off vessels suitable for femorodistal reconstructions(50 in 3). For these preoperative examinations, flow and velocities are often very low indeed. High-frequency transducers are required using low colour and spectral pulse repetition settings.

The tibial-peroneal trunk extends into the calf from the popliteal artery. This segment is another site of predilection of disease and careful assessment is required.

Courtesy of http://www.ultrasoundpaedia.com/normal-leg-arteries/

The PTA: is usually the easier of the two branches of the TPT to locate. Often, it can be localised by placing probe in longitudinal section on medial aspect of mid-calf area behind the tibia, using color or power Doppler to show course of the artery, wich can be followed up and down the calf. The PTA can also be followed as it passes behind the medial malleolus, where its position is constant, and then followed back up the leg.

Scan plane to locate the distal PTA. Courtesy of http://www.ultrasoundpaedia.com/normal-leg-arteries/

The Peroneal artery runs more deeply down the calf than the PTA, lying closer to the post aspect of the tibia and the interosseous membrane. It can be examined from different approaches:1- from posteromedial approach similar to that used for PTA ( in Ipsilateral lateral decubitus position). This artery , by this approach, lies deep and runs parallel to the PTA. 2- It

can also often be seen from the anterolateral approach used for ATA (in supine position) as it runs behind the interosseous membrane. 3-Posterolateral approach (in contolateral Decubitus) may be of value in some cases.

As explained above, The proximal anterior tibial artery can only be followed for a short distance from a posterior approach after the bifurcation of the popliteal artery. The remainder of the vessel can be located and followed distally from anterolateral approach (in supine position) through the extensor muscles lying between the Tibia & Fibula. The two bones can be identified in transverse section and the interosseous membrane located passing between them. The ATA lies on the membrane and can be located on color Doppler, in either the longitudinal or transverse plane. It usually lies nearer the fibula than the tibia. More distally, it can be followed to the level of the ankle.

Courtesy of http://www.ultrasoundpaedia.com/normal-leg-arteries/

In obese or oedematous legs or if blood flow impaired by disease, the PTA & the other arteries of the calf may be difficult to locate. Scanning with Colour doppler in transverse plane using some angulation toward feet or head may show the relative position of PTA and peroneal arteries. Alternatively, the associated veins can be used to identify the region of the relevant artery: Squeezing the foot or lower calf will augment flow in the deep veins, allowing these to be identified in either longitudinal or transverse scan plane. This later approach can be also facilitated if the patient can sit on the edge of the couch with their leg dependent. Using power Doppler may be also of help.

Cross section of calf, showing major relations of calf arteries and three main access points for demonstrating these vessels.

* Scanning Technic: The foot arteries are not usually examined but the Dorsalis Pedis artery may be examined in front of the Ankle Joint, before it passes deep to the metatarsals . This is indicated if the artery is being considered for the insertion of a femorodistal Graft or there are particular questions about the arterial circulation in the foot.

Collateral artery supplying a dorsalis pedis artery. Ultrasound identifies the level of vessel patency and the artery diameter.

Power D improve assessement of smaller vessels of calf & foot. Further Works are necessary to assess echo enhancing agents in the arteries of distal leg and foot vessels.

* Scanning Technic: Aorta and Iliac Arteries

Examination of the iliac vessels is carried out as part of general survey of the lower limb arteries or if the clinical picture suggests a need to confirm or to exclude disease affecting

these vessels or if the the Doppler finding at the groin suggest the likelihood of significant proximal disease.

Some examiners will prepare patients for aorto-iliac Doppler examination with laxatives and low-residue diets to reduce the difficulties caused by gas if it is considered likely that these vessels will be examined, although most center do not do this routinely.

The aorta and proximal iliac vessels are best scanned with a curvilinear or phased array low frequency transducer (2.0-3.5 MHz).

Begin the scan of the abdominal aorta at the level of the xiphisternum, slightly to the left of the midline (or above if the coeliac axis is more proximal). Use both transverse and longitudinal views to measure the maximal anteroposterior and transverse diameter of any aneurysmal dilatation. Document the location of aneurysmal disease with respect to the renal artery ostia. Turning the patient obliquely or into a decubitus position may be necessary to optimize arterial visualization in the presence of extensive bowel gas. Note, in passing, the splanchnic and renal branches of the aorta.

The aortic bifurcation is best seen with the patient turned to the left side and with the transducer placed just in front of the right iliac crest in a longitudinal plane. The distal aorta can usually visualize with the origin of both common iliac arteries. Doppler signals should be obtained from all three vessels at this location. Continue to scan down the common and external iliac arteries

Superiorly, the Common Iliac a. can be identified arising at the aortic bifurcation and then followed distally. Firm pressure with the transducer will displace intervening amount of bowel gaz to a large extent, although care must be taken not to compress the artery and produce a false impression of stenosis.

The Ext Iliac a. can be scanned down from the common iliac a. This artery can, however, most easily be located by continuing to scan proximally from the common femoral artery at the groin (located at a point midway between the midsymphysis pubis and the anterior superior iliac spine) just below the inguinal ligament and moving diagonally toward the umbilicus for a variable distance. The vein lying behind the artery, can be used to identify the probable location of artery , if it is not apparent. Colour or Power Doppler may also help locate the vessel; even if it is not visible on real-time Image.

The internal Iliac a. may be seen arising from the common Iliac a. and passing deeply into the pelvis. This is a useful landmark as visualisation of the internal iliac a. origin, on tracking both the external iliac artery upwards and the common iliac a. downwards, means that the iliac arteries have been examined in their enterity.

The orientation of Iliac arteries as they pass round the pelvis and the use of sector or curved-array Transducers can lead to problems with beam-Vessel geometry and obtaining satisfactory

angles of insonation. However, careful attention to the position of the Transducer will usually allow an appropriate angle to be obtained.

To help evaluate, e.g., the internal and external iliac arteries, the transducer can be placed between the iliac crest and the umbilicus, the patient turning into a lateral decubitus position (side being evaluated up).

If difficulty is encountered in locating the common iliac artery from the aortic bifurcation, it can be followed upward from the external Iliac a.

Doppler waveforms should obtain from the internal and external iliac arteries, noting direction of blood flow and velocity.

At the end of the arterial duplex examination, the ultrasound gel should be removed from the patient with a clean towel, and any excess gel should be removed from the transducer. The transducer should be cleaned using a disinfectant.

* Interpretation and Reporting

Normal Study

– Typical triphasic/biphasic Doppler waveform

– No evidence of plaque, calcification, or aneurysmal dilation on grayscale imaging

– Normal flow velocities

Abnormal Study

– Intraluminal echoes identified

– Abnormal waveforms

– Flow velocity changes

Classification of Stenosis

a- Less than 50%: plaque visualized on grayscale imaging. Triphasic/biphasic waveforms. 30% to 100% increase in PSV compared with that immediately proximal to the site of stenosis.

b- Between 50% and 99%: Plaque visualized. Loss of reverse flow component (variable). More than 100% increase in peak systolic flow velocity compared with that immediately proximal to the site of stenosis. Evidence of poststenotic turbulent/disordered flow. Color flow representation of narrowed flow channel.

c- Complete occlusion: Intraluminal echoes observed throughout vessel. Absence of color and spectral Doppler signals. Reconstitution postocclusion: Resumption of flow visualized by color Doppler and Spectral Doppler flow pattern usually contains both forward and reverse flow elements (influenced by reentry vessel flow).

Descriptions of Plaque/Stenosis

a- Calcified: hyperechoic lesion causing acoustical shadowing.

b- Heterogeneous or complex: lesion of mixed echogenicity causing no acoustical shadowing.

c- Anechoic: hypoechoic, poorly delineated lesion but possibly causing flow disturbance

d-Smooth: surface contour of lesion is smoothly defined.

e- Irregular: rough and irregular luminal surface.

Other Lesions/Syndromes

a- True aneurysm

• Focal dilation of arterial wall

• Pulsating mass seen on grayscale imaging

• Possible visualization of an intimal flap if dissection is present.

• Turbulent flow in the aneurysmal sac

• Intraluminal heterogeneous echoes suggestive of thrombus may be present.

b-False (or pseudo) aneurysm

• Pulsating mass identified on grayscale and color Doppler imaging that is connected to the artery via a “tract”.

• Pattern of reciprocating high-velocity anterograde and retrograde (“to-and-fro”) flow within

the tract

• Turbulent flow is present the body of the false aneurysm (apparent by color and spectral Doppler)

c-Arterial compression syndrome (e.g., popliteal entrapment)

• The artery may have normal appearance and show normal waveform contours at rest.

• Even after exercise, although ankle-brachial values might diminish somewhat, there is often no dramatic change.

• However, if the patient is asked to perform the provocative maneuvers that actually cause pain

(e.g., plantar and dorsiflexion), high-velocity turbulent flow accompanied by visualization of a

temporarily narrowed or obliterated flow channel by color Doppler can be readily seen.

d-Arteriovenous fistula

• Connection between artery and vein identified with color Doppler

• Pulsatile flow identified in the vein distal to the fistula

• Monophasic flow patterns possibly present in the artery proximal to fistula

• High-velocity turbulent flow seen in arteriovenous connection

• Observation of the following findings: 1-An increase in diastolic flow compared with proximal values. 2-High-velocity flow within a persistent vein branch (rather than in the graft itself as in stenosis). 3-Mean velocities in proximal portions of the graft that are significantly higher than those obtained in normal or stenotic grafts. 4-PSVs measured proximal to the fistula that are significantly greater than those measured distally.

Reporting

Ultrasound images are constrained by the transducer width and field of view. This presents difficulties in presenting findings to referring clinicians. It is common to present ultrasound findings on a diagram of the leg, highlighting the presence and size of occlusions and aneurysms, the site and severity of stenoses and major collateral pathways identified at the scan.

II- References

1- The Peripheral Arteries, Paul L Allan in Clinical Doppler Ultrasound, 3d Edition, Myron A Prozniac & Paul L Allan,Chap 4, p.82-104, Churchill Livingstone, 2014, e-book ISBN 9780702055379

2- Evaluation Of Peripheral Arterial Disease Of Lower Limb By Duplex Colour Doppler Study. National Journal of Medical and Dental Research, October-December 2015: Volume-4, Issue-1, Page 41-47

3- Peripheral arteries, Colin R. Deane and David E. Goss in Clinical Ultrasound 3d Edition, Paul L. Allan- Grant M. Baxter- Michael J. Weston, Chap 63, p.1197- 1226, Churchill Livingstone, © 2011 Elsevier Limited. ISBN: 978-0-7020-3131-1.

4- Lower Extremity Arterial Disease in PRINCIPLES of VASCULAR and INTRAVASCULAR ULTRASOUND, Stuart J. Hutchison- Katherine C. Holmes, Chap5, p.96 -132, Copyright © 2012 by Saunders, an imprint of Elsevier Inc., ISBN 978-1-4377-0404-4

5-The Peripheral Arteries , Joseph F. Polak and Jean M. Alessi-Chinetti, in DIAGNOSTIC ULTRASOUND, FOURTH EDITION, Carol M. Rumack – Stephanie R. Wilson- J. William Charboneau- Deborah Levine, Chap 26, p. 998- 1022, Copyright © 2011 by Mosby, Inc., an affiliate of Elsevier Inc.,ISBN: 978-0-323-05397-6.

6- Guidelines for Noninvasive Vascular Laboratory Testing: A Report from the American Society of Echocardiography and the Society of Vascular Medicine and Biology, Gerhard-Herman et al, Journal of the American Society of Echocardiography 2006; 19:955-972, doi:10.1016.

7- ULTRASOUND OF THE LEG ARTERIES – Normal. http://www.ultrasoundpaedia.com/normal-leg-arteries/