Curriculum · Clinical Ultrasound: Multisystem Diagnostic & Point-of-Care Sonography
Vascular Ultrasound: Carotid Duplex & Venous Compression (DVT)
Carotid duplex — gray-scale IMT/plaque, spectral PSV/EDV, and the SRU stenosis criteria with angle correction — and venous compression ultrasound for DVT with waveform phasicity.
~40 min · level: advanced · POCUSVascular draft — pending clinical review
Learning objectives
- Characterize carotid plaque on gray-scale and apply the SRU velocity criteria for internal carotid stenosis.
- Apply the Doppler equation with correct angle correction (≤ 60°) — connecting to the Doppler course.
- Perform compression ultrasound for lower-extremity DVT and recognize normal vs non-compressible veins.
- Interpret venous waveform phasicity and augmentation.
Vascular duplex = gray-scale (wall, plaque, lumen) + color (flow presence/direction) + spectral (pulsed-wave) Doppler (quantitative velocities). The carotid clip below is a longitudinal view of the common carotid with wall plaque.
Reveal findings
- Characterize plaque: surface (smooth/irregular/ulcerated), echogenicity (echolucent/soft = lipid/hemorrhage, higher risk; echogenic/calcified = stable but shadows), and luminal narrowing.
- Intima-media thickness (IMT) is measured on the far wall in plaque-free CCA; > ~0.9 mm is abnormal and a cardiovascular risk marker.
- Gray-scale alone does not grade stenosis — you need spectral velocities (next table).
Stenosis is graded primarily by velocity, because a narrowing accelerates flow (continuity principle, from the Doppler course). Velocities are valid only with angle correction ≤ 60°, the cursor parallel to flow:
| Degree of stenosis | ICA PSV | ICA/CCA PSV ratio | ICA EDV |
|---|---|---|---|
Normal / < 50% | < 125 cm/s | < 2.0 | < 40 cm/s |
50–69% | 125–230 cm/s | 2.0–4.0 | 40–100 cm/s |
≥ 70% (to near-occlusion) |
|
|
|
Near-occlusion | Variable / may be low | Variable | Variable |
Total occlusion | No detectable flow | — | — |
The single most important venous maneuver: with the linear probe in transverse, apply gentle pressure. A normal vein collapses completely (walls touch); an acute thrombus is non-compressible and the vein is often dilated, with echogenic material in the lumen. Interrogate the common femoral, femoral, and popliteal veins (2-point or whole-leg protocols).
| Feature | Normal vein | Acute DVT |
|---|---|---|
Compressibility | Fully compressible | Non-compressible |
Lumen | Anechoic | Echogenic thrombus (may be subtle/acute) |
Caliber | ≈ accompanying artery | Often dilated |
Color fill / flow | Fills, phasic, augments | Filling defect; loss of augmentation |
Worked example — interpreting carotid velocities
ICA PSV = 260 cm/s, ICA EDV = 120 cm/s, ICA/CCA ratio = 4.6, with heterogeneous plaque and color aliasing. What degree of stenosis, and what corroborates it?
All three velocity criteria exceed the ≥ 70% thresholds (PSV > 230, EDV > 100, ratio > 4.0), and the gray-scale plaque plus color aliasing corroborate a hemodynamically significant lesion. This is ≥ 70% ICA stenosis — a finding that, if symptomatic, meets thresholds for considering revascularization.
Key takeaways
- Carotid duplex velocities are valid only with Doppler angle correction at or below 60 degrees because v is proportional to 1/cos(theta), so error explodes as the angle approaches 90 degrees.
- By SRU 2003 criteria, ICA stenosis is 70% or greater when PSV exceeds 230 cm/s, EDV exceeds 100 cm/s, and the ICA/CCA PSV ratio exceeds 4.0; the 50-69% band is PSV 125-230 cm/s with a ratio of 2.0-4.0.
- When systemic factors (cardiac output, contralateral occlusion, tortuosity) distort absolute PSV, the ICA/CCA ratio is the tie-breaker because it normalizes for them.
- Non-compressibility is the single most important sign of acute DVT: a normal vein collapses completely with gentle transverse probe pressure, while an acute thrombus is non-compressible and often dilated with echogenic luminal material.
- Normal venous flow is phasic with respiration and augments with distal squeeze; loss of phasicity (continuous/monophasic flow) suggests a more proximal (iliac/central) obstruction even if the imaged segment compresses normally.
Check your understanding
Registry-style items with worked rationales.
1Carotid duplex velocity measurements require the Doppler angle to be kept at or below:recall
2An ICA peak systolic velocity of 260 cm/s with an ICA/CCA ratio of 4.5 and EDV 110 cm/s corresponds to a stenosis of:application
3During lower-extremity venous compression ultrasound, the single most important finding indicating acute DVT is:application
4Loss of normal respiratory phasicity (continuous/monophasic venous flow) in a leg vein suggests:analysis
Go deeper — trusted free resources
Hand-picked, verified links to authoritative open resources. Opens in a new tab.
Reference article covering the pathology, grading, and Doppler velocity criteria used to diagnose internal carotid artery stenosis.
Focused walkthrough of carotid duplex technique, plaque characterization, and intima-media thickness measurement for atherosclerosis screening.
Reference article on DVT pathophysiology and the sonographic hallmarks of acute versus chronic thrombus.
Point-of-care image atlas and scanning protocol demonstrating venous noncompressibility across the femoral and popliteal compression points.
References
- Grant EG, Benson CB, Moneta GL, et al. Carotid artery stenosis: gray-scale and Doppler US diagnosis — SRU consensus. Radiology. 2003;229(2):340-346.
- American College of Emergency Physicians. Ultrasound Guidelines: Emergency, Point-of-care, and Clinical Ultrasound Guidelines in Medicine. 2016/2023.
- Moore CL, Copel JA. Point-of-care ultrasonography. N Engl J Med. 2011;364(8):749-757.
- Kremkau FW. Sonography Principles and Instruments. 9th ed. Elsevier; 2016.