Accepted Guidelines for a Normal TCD Study
| Artery | Window | Depth (mm) | Direction | Mean Flow Velocity |
|---|---|---|---|---|
| MCA | Temporal | 30 to 60 | Toward probe | 55 ± 12 cm/s |
| ACA | Temporal | 60 to 85 | Away | 50 ± 11 cm/s |
| PCA | Temporal | 60 to 70 | Bidirectional | 40 ± 10 cm/s |
| TICA | Temporal | 55 to 65 | Toward | 39 ± 09 cm/s |
| ICA (siphon) | Orbital | 60 to 80 | Bidirectional | 45 ± 15 cm/s |
| OA | Orbital | 40 to 60 | Toward | 20 ± 10 cm/s |
| VA | Occipital | 60 to 80 | Away | 38 ± 10 cm/s |
| BA | Occipital | 80 to 110 | Away | 41 ± 10 cm/s |
TCD, transcranial Doppler; MCA, middle cerebral artery; ACA, anterior cerebral artery; PCA, posterior cerebral artery; TICA, terminal internal carotid artery; ICA, internal carotid artery; OA, ophthalmic artery; VR, vertebral artery; BA, basilar artery.