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Radiology • Vascular Ultrasound

Carotid Doppler Ultrasound

Also called: Carotid Duplex • Neck-Artery Ultrasound • Carotid Stenosis Scan

Carotid Doppler examines the main arteries in the neck that carry blood towards the brain and eyes. It shows plaque, narrowing or blockage and measures how blood flows through each accessible segment.

It is useful after selected TIA or stroke presentations and for surveillance, but it does not image brain tissue or rule out an acute stroke. New neurological symptoms require emergency assessment immediately.

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Stroke and TIA symptoms are medical emergencies

Do Not Wait for a Carotid Scan if Symptoms Start Suddenly

Call emergency services immediately for any sudden:

  • Drooping or weakness on one side of the face.
  • Weakness, numbness or loss of coordination in one arm or leg.
  • Slurred speech, inability to speak, confusion or difficulty understanding words.
  • Loss, blurring or a curtain-like shadow in one eye, or new double vision.
  • Severe imbalance, inability to walk, collapse or an unusually severe headache with neurological symptoms.

Note the time symptoms began and do not drive yourself. Emergency assessment is still required if the symptoms improve or disappear, because this may be a transient ischaemic attack (TIA) and the risk of a subsequent stroke can be highest early on.

Carotid ultrasound may be arranged urgently after specialist assessment, but it must not delay brain imaging, medical treatment or a stroke/TIA pathway. A normal carotid scan does not exclude stroke.

What is Carotid Duplex Ultrasound?

A handheld probe sends high-frequency sound waves through gel on the neck. Grey-scale ultrasound shows the artery wall and plaque. Colour Doppler displays moving blood, while spectral Doppler creates waveforms and measures blood-flow velocity at selected points.

The scan evaluates both sides of the neck. A focal narrowing accelerates blood through the smaller channel and changes the waveform. The radiologist combines velocity, ratios, colour flow and the visible lumen to estimate stenosis rather than relying on a single number.

Carotid Plaque is One Possible Source of Stroke—Not the Only One

Stroke and TIA can arise from the heart, small brain vessels, other arteries, blood disorders and several less common causes. A carotid scan answers a neck-artery question; ECG, brain imaging, cardiac assessment and laboratory tests may remain essential even when the carotids are normal.

Why Might the Scan Be Requested?

After TIA or stroke To identify clinically important carotid stenosis when the result may alter treatment.
Temporary vision loss To assess an appropriate carotid source after urgent neurological or eye evaluation.
Carotid bruit To determine whether a neck sound on examination corresponds to significant arterial disease.
Known carotid disease To monitor selected stenosis or compare with a previous scan according to a clinical plan.

Other indications can include:

  • Follow-up after carotid endarterectomy, angioplasty or stent placement.
  • Assessment before selected heart or major vascular procedures when clinically indicated.
  • Suspected carotid dissection or another arterial abnormality, although CTA or MRA may be preferred urgently.
  • Evaluation of accessible vertebral-artery direction and waveform in selected posterior-circulation questions.
  • Surveillance of a previously documented plaque, stenosis, occlusion or reconstruction.
  • Clarification after another examination suggests carotid or neck-vessel disease.

Carotid ultrasound is not a general explanation for every episode of dizziness, fainting, headache or poor balance. These symptoms have many causes, and the referring clinician should select imaging based on the neurological pattern and examination rather than the word “dizziness” alone.

What Does the Scan Examine?

Common carotid arteries The main arteries ascending each side of the neck are assessed for wall change, plaque, waveform and disease affecting blood entering the carotid bifurcation.
Carotid bulb and bifurcation This widening is where the common carotid divides and where atherosclerotic plaque frequently forms. Plaque location, surface and effect on the lumen are documented where visible.
Internal carotid arteries These supply the brain and eyes. The accessible cervical segments are evaluated for plaque, stenosis, near-occlusion, occlusion and abnormal flow patterns.
External carotid arteries These mainly supply the face and scalp. They help identify the bifurcation branches and may provide collateral flow when internal carotid disease is severe.
Vertebral arteries where accessible Direction and waveform may be recorded in the neck. Carotid duplex does not examine the complete vertebral course or all posterior-circulation arteries within the skull.
Plaque characteristics Distribution, echogenicity, calcification and surface appearance may be described. Ultrasound cannot determine the microscopic composition or future behaviour of plaque with certainty.
Velocity and ratios Peak systolic velocity, end-diastolic velocity and selected internal-to-common carotid ratios help classify narrowing when combined with direct images and downstream waveform findings.
Previous treatment An endarterectomy site or stent is assessed for patency, recurrent narrowing and altered velocity patterns using criteria appropriate to the reconstruction and local surveillance protocol.

How is Carotid Narrowing Graded?

Reports commonly group internal carotid stenosis into broad categories such as no significant narrowing, mild disease, moderate stenosis, severe stenosis, near-occlusion or complete occlusion. The precise terminology and percentage method may follow validated laboratory criteria.

Visible lumen and plaque The radiologist looks directly at how plaque affects the residual channel, although calcification and vessel angle can prevent an accurate diameter measurement in some segments.
Peak systolic velocity Blood generally travels faster through a significant focal narrowing. Sampling technique and correction for the direction of flow are important for reliable comparison.
End-diastolic velocity and ratios Additional velocity measurements and an ICA-to-CCA ratio support classification, particularly when the appearance and peak velocity do not agree perfectly.
Near-occlusion is different A critically narrowed artery may have a very small distal lumen and unexpectedly low rather than very high flow. CTA, MRA or specialist review may be required for confirmation.

A percentage is not interpreted in isolation. Whether symptoms occurred recently, which side is affected, age, health, brain imaging and treatment risk all influence management. Do not compare percentages from different modalities without knowing whether the same measurement method was used.

How Should I Prepare?

Carotid Doppler requires little or no special preparation. You can usually eat, drink and take regular medicines normally unless another test is booked at the same visit.

Clothing Wear a loose, open-necked shirt or blouse. A high collar, tight neck, tie or roll-neck must be moved or removed so the probe can reach from the collarbone to below the jaw.
Jewellery and hearing devices Remove necklaces and large earrings if possible. Tell the team about a hearing aid or device near the scanning area so it can be protected or repositioned safely.
Medicines Do not stop antiplatelet, anticoagulant, cholesterol-lowering, blood-pressure or diabetes treatment for an external ultrasound unless the treating clinician specifically instructs you.
Neck comfort and mobility Tell the team if you cannot lie flat or turn your head because of pain, breathlessness, recent surgery, a cervical-spine condition, tracheostomy or another limitation. Position can be adapted.
  • Bring the referral and previous carotid ultrasound, CTA, MRA or angiography reports.
  • Bring details of any TIA, stroke, eye symptoms, carotid endarterectomy or stent—including side and date.
  • Bring an accurate medicine list and relevant discharge or specialist letters.
  • Do not apply heavy cream or oil to the neck immediately before the scan if this can be avoided.
  • Tell the team about dressings, infection, fragile skin, a central line or severe neck tenderness.

What Happens During the Scan?

1 The clinical question is reviewed

The radiologist confirms symptoms, side, timing, vascular risk factors, previous imaging and any carotid operation or stent relevant to interpretation.

2 You lie on the examination couch

The neck is exposed while clothing is protected. You usually lie on your back with the head supported and turned slightly away from the side being examined.

3 Gel and the probe are applied

Water-based gel is placed along the side of the neck. The probe moves gently from the collarbone towards the jaw, using light pressure for contact and different angles for difficult segments.

4 Both carotid systems are examined

Grey-scale and colour images document the arteries and any plaque. The same structured assessment is performed on both sides even when symptoms or previous disease are one-sided.

5 Velocities and waveforms are recorded

Doppler samples are obtained at standard points and any suspected narrowing. You may hear amplified pulsing or “whooshing” sounds generated from the blood-flow signal.

6 Images are reviewed and reported

The radiologist integrates plaque, lumen, colour and velocity criteria. Urgent significant findings are communicated through the appropriate stroke, vascular or referring pathway.

The examination commonly takes about 20–30 minutes. A high carotid bifurcation, calcified plaque, difficult neck movement, previous surgery or a stent can make it longer.

What Do Common Report Terms Mean?

Atheromatous plaque A deposit of lipid, fibrous tissue and sometimes calcium within the arterial wall. Plaque may be present without creating a haemodynamically significant stenosis.
Calcified plaque / acoustic shadowing Calcium appears bright and can block the sound beam, hiding part of the lumen. Velocity and another imaging modality may be needed when shadowing prevents confident grading.
Heterogeneous plaque The plaque contains areas with different ultrasound appearances. This description does not by itself determine that a procedure is needed or predict exactly when a stroke will occur.
Stenosis The artery is narrowed but remains open. Reports classify severity using visible lumen, velocities, ratios and other waveform findings according to validated criteria.
PSV / EDV Peak systolic velocity and end-diastolic velocity are speeds measured at different phases of the heartbeat. They support grading but are not interpreted alone.
ICA / CCA ratio Internal carotid peak velocity is compared with common carotid velocity. The ratio helps account for general flow differences and supports stenosis classification.
Spectral broadening / turbulence Blood has a wider range of velocities and disturbed flow, often at or beyond a narrowing. It is interpreted with plaque, peak velocity and the vessel's geometry.
Near-occlusion The residual channel is critically small and the artery beyond may collapse. Flow can be unusually low, so confirmatory angiographic imaging may be recommended.
Occlusion No patent lumen or flow is demonstrated in the assessed internal carotid segment. Treatment differs from stenosis and requires specialist interpretation with symptoms and other imaging.
Antegrade / retrograde vertebral flow Antegrade means flow is towards the brain. Reversed or alternating flow can suggest a steal pattern from proximal subclavian disease and is correlated with arm pressures and symptoms.

What Can Carotid Doppler Not Determine Reliably?

  • Whether brain tissue is currently having an acute stroke or has already been injured.
  • All causes of TIA, stroke, dizziness, fainting, headache or visual disturbance.
  • The complete arteries inside the skull or the full vertebrobasilar circulation.
  • Segments behind the jaw, chest or dense calcification that sound waves cannot reach clearly.
  • The microscopic composition or exact future behaviour of an individual plaque.
  • Whether a carotid procedure is appropriate from a percentage alone.
  • Exact equivalence between ultrasound and CTA/MRA stenosis percentages when methods differ.
  • Every segment when a short neck, deep vessel, dressing, line, severe pain or limited movement restricts access.

CTA, MRA, catheter angiography, brain imaging or cardiac investigations may still be required when the ultrasound is technically limited, symptoms and findings do not match or an intervention is being planned.

What Happens After the Scan?

The gel is wiped away and you can return to normal meals, medicines and activity. The radiologist prepares a formal report describing plaque, stenosis category, flow direction, technical limitations and relevant comparison with previous imaging.

A recent TIA or stroke with significant narrowing may require urgent specialist action. For stable or asymptomatic disease, the clinician considers symptoms, severity, age, other illnesses, brain imaging and procedure risk before recommending surveillance, medical treatment or an intervention.

Do not start or stop antiplatelet, anticoagulant, cholesterol-lowering or blood-pressure medicines solely from the scan report. Seek emergency care for any new stroke or TIA symptoms while awaiting follow-up.

Myth vs Fact

Myth Carotid disease always causes neck pain.
Fact Plaque and stenosis are usually painless. Symptoms, when they occur, relate to reduced or interrupted blood supply to the brain or eye rather than pain over the artery.
Myth A carotid bruit proves there is severe narrowing.
Fact A bruit can occur with moderate disease or transmitted heart sounds, and severe narrowing may be silent. Duplex determines whether important stenosis is actually present.
Myth A normal carotid scan excludes stroke and TIA.
Fact Many strokes arise from the heart, small brain vessels or other causes. Neurological symptoms still need urgent specialist assessment and appropriate brain and cardiac testing.
Myth Colour Doppler uses injected dye and radiation.
Fact The machine creates colour from the movement of blood detected by sound waves. Routine carotid duplex uses no injection, contrast material or ionising radiation.

Frequently Asked Questions

Do I need to fast for carotid Doppler?

No. Eat, drink and take regular medicines normally unless another examination is booked at the same visit. Wear a loose, open-necked top and remove necklaces before the scan.

Should I stop an antiplatelet or blood-thinning medicine?

No. Do not stop prescribed antiplatelet or anticoagulant medicine for an external ultrasound unless your treating clinician specifically instructs you.

Is the scan painful?

It is usually painless. Light probe pressure near the jaw or over a tender surgical scar can be uncomfortable. Tell the radiologist so position and pressure can be adjusted.

Will both sides of my neck be scanned?

Yes, usually. Both carotid systems are assessed for comparison and because disease can be present on the side opposite the recent symptoms.

Can a carotid scan diagnose a stroke?

No. It can identify neck-artery disease that may contribute to stroke risk, but brain imaging and neurological assessment diagnose and classify a stroke. Sudden symptoms require emergency care.

Should dizziness alone lead to carotid ultrasound?

Not routinely. Dizziness has many causes and isolated dizziness is not the typical pattern of carotid TIA. A clinician should assess the complete symptom pattern and choose the appropriate test.

Why might CTA or MRA be recommended afterwards?

Angiographic imaging may confirm severe or near-occlusive disease, show regions hidden by calcium or the jaw and provide a wider map before treatment planning.

Does a stenosis percentage automatically mean surgery is needed?

No. Recent symptoms, side, severity, age, overall health, brain imaging and procedural risk all matter. A stroke or vascular specialist interprets the result and discusses appropriate options.

When will I receive the result?

The radiologist prepares a report for the referring clinician. Urgent findings are communicated through the appropriate pathway. Ask before leaving how and when the result will be discussed.

Other Ultrasound Guides

Each Doppler protocol evaluates a different circulation. The original referral helps ensure the correct arteries or veins are examined.

Radiology Arterial Doppler Ultrasound Lower-Limb Arterial Duplex / PAD Scan Read scan guide → Radiology Venous Doppler Ultrasound DVT Scan / Varicose-Vein Reflux Study Read scan guide → Radiology Thyroid Ultrasound USG Thyroid / Neck Ultrasound Read scan guide → Radiology USG Abdomen Abdominal / Whole-Abdomen Ultrasound Read scan guide →

A Note From Our Doctors

The information on this page is intended to help you understand your condition. It should not be considered a diagnosis or a substitute for a consultation with a qualified medical professional.

Every patient is unique. The same symptom can have different causes in different individuals, and the most appropriate investigations and treatment depend on your medical history, examination findings, age, existing medical conditions and test results.

At SR Speciality Hospital, we believe in treating the whole patient—not just a symptom, scan or laboratory report. Every treatment plan is individualised after careful medical evaluation.

Radiology Appointments

Have you been advised to undergo carotid Doppler?

Contact the hospital with the exact referral and bring previous vascular imaging. New stroke or TIA symptoms require emergency assessment rather than a routine outpatient appointment.

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