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