Carotid Doppler Ultrasound

Carotid duplex ultrasound combines B-mode imaging with color and spectral Doppler to evaluate the extracranial carotid and vertebral arteries for atherosclerotic disease. It quantifies internal carotid artery stenosis using velocity criteria and characterizes plaque, guiding decisions on carotid endarterectomy or stenting. It is the first-line, noninvasive test in the workup of stroke, TIA, and asymptomatic bruit.

Indications

Recent stroke, transient ischemic attack, or amaurosis fugax
Asymptomatic cervical bruit
Screening in patients with significant atherosclerotic risk factors or before major cardiovascular surgery
Surveillance following carotid endarterectomy or stenting
Follow-up of known carotid stenosis
Evaluation of pulsatile neck mass or suspected carotid dissection
Assessment of subclavian steal with vertebral artery flow direction

Contraindications & Cautions

No contraindications; noninvasive and radiation-free
Extensive vessel calcification causes acoustic shadowing and can preclude accurate velocity measurement
High carotid bifurcation or short thick neck may limit access
Not reliable for intracranial or ostial great-vessel disease; CTA or MRA may be needed
Follow ALARA for Doppler exposure

Patient Preparation

No fasting or specific preparation required
Supine positioning with the head slightly extended and turned away from the side being examined
Remove neck jewelry and high collars
No consent required for diagnostic scanning
Document blood pressure and relevant symptoms and laterality

Technique & Parameters

High-frequency linear transducer (5-7 MHz); lower frequency for deep or large necks
Grayscale survey of common, internal, and external carotid arteries and vertebral arteries in transverse and longitudinal planes
Characterize plaque location, extent, surface, and echogenicity
Color Doppler to identify flow, turbulence, and areas of aliasing
Spectral Doppler with angle correction at 60 degrees or less measuring peak systolic velocity (PSV) and end-diastolic velocity (EDV) in the CCA, ICA, and ECA
Calculate ICA/CCA PSV ratio
Determine vertebral artery flow direction (antegrade versus retrograde)
Apply the Society of Radiologists in Ultrasound consensus velocity criteria

Systematic Review

Common carotid artery: intima-media thickness, plaque, velocities
Carotid bulb and bifurcation: plaque burden and surface characteristics
Internal carotid artery: PSV, EDV, spectral broadening, degree of stenosis
External carotid artery: identify by branches and temporal tap to distinguish from ICA
ICA/CCA PSV ratio
Vertebral arteries: presence, direction of flow, and velocities
Plaque morphology: calcified, echolucent, ulcerated, heterogeneous
Post-intervention: stent patency, in-stent velocities, endarterectomy site

Key Findings & Significance

ICA PSV <125 cm/s with no plaque indicates normal or <50% stenosis
ICA PSV 125-230 cm/s indicates 50-69% stenosis
ICA PSV >230 cm/s with EDV >100 cm/s and ICA/CCA ratio >4 indicates 70-99% stenosis
Absence of flow with a visible lumen thrombus indicates occlusion
String sign of trickle flow indicates near-occlusion
Retrograde vertebral flow indicates subclavian steal
Echolucent, irregular, or ulcerated plaque carries higher embolic risk

Differential Considerations

Elevated ICA velocity: true stenosis, tortuosity, contralateral occlusion causing compensatory flow, or post-stenotic hyperemia
Absent ICA flow: occlusion versus near-occlusion versus technical artifact from calcification
Low CCA velocities: proximal common carotid or innominate stenosis, cardiac dysfunction, aortic stenosis
Pulsatile neck mass: tortuous carotid, aneurysm, carotid body tumor, dissection
Retrograde vertebral flow: subclavian steal from proximal subclavian stenosis
Elevated velocities post-stenting: in-stent restenosis versus normal stent-related velocity elevation

Pearls & Pitfalls

Distinguish ICA from ECA using branch pattern, waveform, and the temporal tap maneuver
Contralateral high-grade stenosis or occlusion elevates ipsilateral ICA velocities and can cause overestimation
Heavy calcification shadows the vessel; report velocities as limited and consider CTA/MRA
Maintain a Doppler angle of 60 degrees or less to keep velocity measurements accurate
Near-occlusion may show paradoxically low velocities; grayscale and color confirm the trickle of flow
Report plaque morphology, as ulcerated or echolucent plaque is clinically relevant beyond stenosis grade
Post-endarterectomy and post-stent studies use different velocity thresholds

Structured Report

State indication and symptomatic laterality
Report plaque location, extent, and morphology bilaterally
Report PSV and EDV for CCA, ICA, and ECA, and the ICA/CCA ratio
State the degree of stenosis category for each ICA per consensus criteria
Report vertebral artery flow direction and any subclavian steal
Note technical limitations such as calcification
Impression: degree of stenosis per side with recommendation for surgical/endovascular referral or surveillance interval

References

Grant EG et al. Carotid Artery Stenosis: Grayscale and Doppler Ultrasound Diagnosis - Society of Radiologists in Ultrasound Consensus Conference
NASCET (North American Symptomatic Carotid Endarterectomy Trial) stenosis measurement
ACR-AIUM-SRU Practice Parameter for the Performance of an Ultrasound Examination of the Extracranial Cerebrovascular System
ACR Appropriateness Criteria: Cerebrovascular Disease

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

Carotid Doppler Ultrasound

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References