Skip to main content

Table 1 Common parameters derived from transcranial Doppler

From: How I use Transcranial Doppler

 Abbreviation or formulaNormal valuesElevated ICPBrain deathCerebral autoregulationCerebral vasospasm
Pulsatility indexPI = (sFV − dFV)/mFV< 1.4> 1.4
Mean FVmFV60–80 cm/s [2]Mild ≥ 120 cm/s
Moderate = 120–200 cm/s
Severe ≥ 200 cm/s (with LR < 3)
Diastolic FVdFV> 20 cm/s< 20 cm/sNegative or absentIncreased
Mean flow indexMx< 0.3> 0.3> 0.3 (impaired)> 0.3
Lindegaard ratioLR = mFV MCA/mFV extracranial ICA< 3Mild ≥ 3
Moderate = 3–6
Severe ≥ 6
THR test    Less than 10% increase from baseline sFV (impaired) 
  1. FV flow velocity, MCA middle cerebral artery, ICA internal carotid artery, Mx mean flow index, dFV diastolic flow velocity, mFV mean flow velocity, sFV systolic flow velocity, CA cerebral autoregulation, THR transient hyperemic test