Version July 2025
| Degree of stenosis (%) | Primary parameters | Additional parameters | ||
| ICA PSV (cm/sec) | Plaque estimate (%)* | ICA/CCA PSV ratio | ICA EDV (cm/sec) | |
| Normal | <125 | None | <2.0 | <40 |
| <50 | <125 | <50 | <2.0 | <40 |
| 50 to 69 | 125 to 230 | ≥50 | 2.0 to 4.0 | 40 to 100 |
| ≥70 but less than near occlusion | >230 | ≥50 | >4.0 | >100 |
| Near occlusion | High, low, or undetectable | Visible | Variable | Variable |
| Total occlusion | Undetectable | Visible, no detectable lumen | Not applicable | Not applicable |
CCA: common carotid artery; EDV: end diastolic velocity; ICA: internal carotid artery; PSV: peak systolic velocity; US: ultrasound.
* Plaque estimate (diameter reduction) with grayscale and color Doppler US.