Studies in Rheoencephalography (REG)

Abstract

This article presents an overview of rheoencephalography (REG) -electrical impedance measurements of the brain -and summarizes past and ongoing research to develop medical applications of REG for neuro-critical care and for primary prevention of stroke and cardiovascular disease. The availability of advanced electronics and computation has opened up the potential for use of REG technology as a noninvasive, continuous and inexpensive brain monitor for military and civilian applications. The clinical background information presented here introduces physiological and clinical environments where REG has potential for use in research and clinical settings.REG studies over the past three decades have involved in vitro and in vivo groups (animal and human), including more than 1500 measurements and related electronic and computational results and practical applications. In vitro studies helped researchers understand the flow/volume relationship between Doppler ultrasound and electrical impedance signals and supported development of REG data processing methods. In animal studies, REG was used to monitor the lower limit of cerebral blood flow (CBF) autoregulation (AR) using a newly developed algorithm. These animal studies also confirmed correlations between REG and measurements of carotid flow (CF) and intracranial pressure (ICP). Human studies confirmed the applicability of REG for detecting cerebrovascular alteration, demonstrating the usefulness of REG in the field of stroke/cardio-vascular disease prevention. In these studies, REG was compared to known stroke risk factors and to results obtained using carotid ultrasound measurements. An intelligent REG system (Cerberus) has been developed for primary stroke prevention. In these studies, the biologically relevant variables of the REG signal were pulse amplitude (minimummaximum distance) and duration of the anacrotic (rising) portion of the REG pulse wave.The principal limitation of REG for clinical application is the lack of pathological and physiological correlations. The studies presented here have initiated such inquiries, but many clinical questions about the pathophysiological background of REG remain unanswered.These results demonstrate that REG development is a multidisciplinary subject with relevance for medicine (vascular neurology and neurosurgery intensive care); electronic engineering; mathematics, and computer science (data processing). It is hoped that information presented in this article will provide assistance to those involved in REG research, particularly in development and clinical applications.

Full-body visible human project^® female computational phantom and its applications for biomedical electromagnetic modeling

“…Other very recent applications of the VHP-Female model, including the simulation of electrode voltage/current response to CSF pulsations in Rheoencephalography [23], will be presented.…”

Comparison of cerebrovascular reactivity tests: a pilot human study

“…In previous studies, we reported results of correlative studies indicating that REG has potential for use in neuro-monitoring [25]. A previous study documented that REG (REGx) and ICP (PRx) has high correlation in order to detect the lower limit of CBF autoregulation [4].…”

Modelling the Ability of Rheoencephalography to Measure Cerebral Blood Flow

“…The final model was made of 57215 nodes and 261827 finite tetrahedra elements. Next, all finite elements were assigned to the electrical conductivity and permittivity values according to the amount of the particular tissue inside the tetrahedra (1).…”

“…Due to the fact that REG is widely used in routine clinical studies and has a long history of practical applications, the ability of REG to assess the functional state of the human brain has been well investigated. Despite this fact, the method is frequently referred to as unreliable and controversial because the measurements are ambiguous with a high risk of clinical misinterpretation [1].…”