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Carotid ICA/CCA PSV Ratio

Grades internal carotid artery stenosis on Doppler ultrasound by combining ICA peak systolic velocity with the ICA/CCA velocity ratio (SRU consensus).

The 2003 Society of Radiologists in Ultrasound (SRU) consensus grades internal carotid artery stenosis primarily on ICA peak systolic velocity, with the ICA/CCA PSV ratio and ICA end-diastolic velocity as supportive parameters. The ratio helps when the PSV is confounded by contralateral occlusion, cardiac output or tortuosity.

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📐 Formula

ICA/CCA ratio = ICA peak systolic velocity / CCA peak systolic velocity

When to Use

  • Carotid duplex ultrasound in patients with a bruit, TIA/stroke, or for surveillance of known plaque.
  • When absolute PSV may be unreliable (low cardiac output, contralateral high-grade stenosis/occlusion).
  • Pre-operative grading before carotid endarterectomy or stenting.

How It Works

  • Record the highest ICA peak systolic velocity across the plaque with angle-corrected Doppler (≤ 60°).
  • Record the CCA peak systolic velocity 2–3 cm proximal to the bifurcation.
  • Compute the ICA/CCA ratio and combine with the ICA PSV band.

Interpreting the Result

  • ICA PSV < 125 cm/s and ratio < 2.0: < 50% stenosis (or normal).
  • ICA PSV 125–230 cm/s or ratio 2.0–4.0: 50–69% stenosis.
  • ICA PSV > 230 cm/s or ratio > 4.0: 70–99% (near-occlusive) stenosis.
  • Markedly reduced or absent flow with a trickle signal suggests near-occlusion; absent flow indicates total occlusion.

Limitations & Pitfalls

  • Velocity thresholds are laboratory-dependent and should ideally be internally validated against angiography.
  • Heavily calcified plaque, tandem lesions and contralateral occlusion can alter velocities.
  • Does not replace CTA/MRA/DSA for surgical decision-making in borderline cases.

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.
  • AbuRahma AF, Srivastava M, Stone PA, et al. Critical appraisal of the Carotid Duplus consensus criteria. J Vasc Surg. 2011;53(1):53-59.

⚕️ For clinical decision support only. Always verify calculations and apply clinical judgment.