Carotid Duplex Ultrasound

1. 1

   Patient supine, head slightly turned away from side being scanned. Use linear probe (5–12 MHz).

2. 2

   Begin with CCA transverse sweep from clavicle to bifurcation — survey for plaque, IMT, and diameter.

3. 3

   Longitudinal CCA: angle ≤60° to vessel, sample Doppler at proximal, mid, and distal. Document PSV and EDV.

4. 4

   At bifurcation: identify ICA (posterior, larger, no branches) and ECA (anterior, smaller, branches). Use temporal tap test to confirm.

5. 5

   Longitudinal ICA: sample at origin, proximal, mid, and distal. Calculate ICA/CCA PSV ratio.

6. 6

   Measure IMT at far wall of distal CCA, 1cm proximal to bifurcation in a plaque-free segment.

7. 7

   Vertebral artery: probe posterolateral to CCA between transverse processes. Confirm antegrade flow. Repeat all steps contralateral side.

• CCA — transverse sweep (proximal to bifurcation)
• CCA — sagittal + Doppler (proximal, mid, distal)
• Bifurcation — grayscale + Doppler
• ICA — sagittal + Doppler (proximal, mid, distal)
• ECA — sagittal + Doppler
• Vertebral artery — sagittal + Doppler (bilateral)
• Repeat contralateral side

• Intimal-medial thickness (IMT)
• Plaque (location, echogenicity, surface)
• PSV/EDV at CCA, ICA, ECA
• ICA/CCA PSV ratio
• Vertebral flow direction

• Doppler angle must not exceed 60° — perpendicular angles are contraindicated
• Distinguish physiologic bifurcation turbulence from pathologic stenosis
• Retrograde vertebral flow = subclavian steal syndrome

Temporal artery tap test: brief tapping on the superficial temporal artery creates a 'bouncing' waveform in the ECA — confirms ICA vs. ECA identity.