Transcranial Doppler

Mean velocities >100 cm/sec are reported to have high accuracy in detecting >50% diameter reduction stenoses.

Relative increase in PSV of >30% compared to same segment on contralateral side is suspicious for hemodynamically significant stenosis and increase of >50% is highly definitive for stenosis.

Typical Doppler waveform features in presence of stenosis: increased velocity; flow disturbance, covibration phenomena (vibration of vessel wall and surrounding soft tissue).