Quantification of intracranial contribution to rheoencephalography by a numerical model of the head

Objectives: Partial contributions of intracranial and extracranial circulat ion to rheoencephalography (REG) remain uncertain. The main goal of this wo rk is to determine theoretically the capability of REG techniques to reflec t intracranial blood how. Methods: Head and current injection electrodes were computationally modeled to assess REG sensitivity to brain and scalp conductivity changes. Data ob tained were related to tissue perfusions to calculate the partial contribut ion of cerebral blood perfusion to REG I, REG II and monopolar REG and to a ssess their amplitudes. Results: When REG I and monopolar REG were used, the theoretical maximum of intracranial contribution was reached with large current injection electro des, being 8% for REG I and 12% for monopolar REG. However, some specific R EG II electrode arrangements showed a nil contribution of the extracranial circulation and a minimum influence of the electrode size. Conclusions: These results may explain the disagreement on REG origin and s uggest a theoretically optimum electrode arrangement. (C) 2000 Elsevier Sci ence Ireland Ltd. All rights reserved.