What is a Carotid Ultrasound?
A carotid ultrasound (also called carotid duplex Doppler ultrasound) is a noninvasive imaging test that uses sound waves to evaluate the carotid arteries in your neck for atherosclerotic plaque, stenosis (narrowing), and blood flow abnormalities to assess stroke risk. 1, 2
How It Works
The examination combines two ultrasound techniques 2, 3:
- Gray-scale (B-mode) imaging: Visualizes the artery structure, plaque presence, and measures intima-media thickness (IMT)
- Doppler ultrasound: Measures blood flow velocity and direction using sound wave frequency shifts
The test specifically evaluates the common carotid artery and internal carotid artery (ICA) for stenosis severity using velocity criteria, with current thresholds of peak systolic velocity ≥180 cm/s indicating 50-69% stenosis 2.
What It Detects
Carotid ultrasound identifies 2, 4, 3:
- Atherosclerotic plaque: Presence, extent, and characteristics (stable vs. unstable morphology)
- Degree of stenosis: Mild (<50%), moderate (50-69%), or severe (70-99%) narrowing
- Plaque vulnerability: Hypoechoic (unstable), ulcerated, or mobile plaques associated with higher stroke risk
- Intima-media thickness: Marker of atherosclerotic burden
- Complete occlusion: Total blockage of the artery
Clinical Applications
The test is appropriate for 5, 1:
- Patients with symptoms of cerebrovascular disease (stroke, TIA, neurologic deficits)
- Candidates for carotid endarterectomy or stenting within 48 hours of TIA/minor stroke
- Surveillance of known carotid stenosis (every 12 months for moderate stenosis, every 6-12 months for severe stenosis)
- Evaluation of carotid artery dissection from aortic arch extension
Screening asymptomatic patients is generally not recommended unless they have multiple atherosclerotic risk factors (diabetes, age >65, smoking, hypercholesterolemia) and are candidates for intervention 5, 6, 7.
Key Advantages
- Simple, safe, and noninvasive
- No radiation exposure
- No contrast material required
- Cost-effective
- Repeatable for surveillance
- Can be performed at bedside
Important Limitations
The test has specific constraints 5, 8:
- Cannot reliably detect distal internal carotid artery dissection from trauma (use MRA or CTA instead)
- Results depend heavily on operator technique and Doppler angle settings
- May not adequately visualize vertebral artery stenosis (other imaging preferred)
- Physical challenges like calcified plaque or patient body habitus can limit accuracy