Extracranial Stenosis Criteria

**Velocity criteria used for ICA not used for CCA and ECA**

Common Carotid Artery Normal -

No velocity increase

No visible plaque seen on the B mode image

<50% diameter reduction -

Presence of plaque seen on the B mode image

Wall thickening or irregularity with or without flow disturbance

No focal velocity increase

>50% diameter reduction -

Focal velocity increase of at least 100%

Post-stenotic turbulence

Presence of plaque seen on the B mode image

Total Occlusion -

Clearly identified vessel with no Doppler signals

External Carotid Artery

Significant stenosis > 300 cm/sec

Vertebral Artery Normal -

Antegrade flow

<50% diameter reduction -

No focal velocity increase

>50% diameter reduction -

Focal velocity increase of at least 100%

Post-stenotic turbulence