Evaluation of consistency among different electrical impedance indices of relative cerebral blood flow in normal resting individuals.

Significant correlation was observed, in normal resting individuals, of interregional variation of classical amplitude-dependent electrical impedance indices of cerebral blood flow (CBF) with three quantitative rheographic measures of cerebral blood flow which have been themselves radioisotopically validated. Since these amplitude-related CBF indices are derived from the Nyboer model relating blood volume changes to change of impedance, the data support the correctness and applicability of this model to the head. Interrelationship among the CBF parameters obtained with the use of this technique was found to be markedly affected by differing electrode placements; it was not apparently affected by extracranial circulation. It is concluded that under proper recording conditions, several assumptions underlying rheoencephalography are consistent and that it may be a useful tool for the study of relative regional cerebral blood flow in normal individuals.