[Flow index of transcranial Doppler sonography].

A flow index calculated by multiplying mean velocity (v) by signal power is proposed for use in dynamic transcranial Doppler studies. Contrary to velocity this index indicates the relative changes in volume flow even in case of change in diameter of the vessel examined. A CO2 respiration experiment is reported on, in which a simplified flow index (vmax.p) was calculated off-line, and indicated an increase of the caliber of the middle cerebral artery with increased pCO2.