Influence of the scalp thickness on the intracranial contribution to rheoencephalography

Pérez, Juan Alberto Tormos; Guijarro, Enrique; Barcia, Juan A.

doi:10.1088/0031-9155/49/18/013

Cited by 12 publications

(9 citation statements)

References 26 publications

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“…This monkey study demonstrates that with surface electrodes (non invasive), the slow wave oscillations of the REG signal are present (not filtered out by the skull) and with specialized algorithms, REG can be used to detect lower limit of CBF AR. This result worth to compare with those of others discribing the influence of scalp influence on REG [74][75][76][77].…”

Section: Lower Limit Of Cbf Autoregulationsupporting

confidence: 60%

Studies in Rheoencephalography (REG)

Bodó

2010

Journal of Electrical Bioimpedance

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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.

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Section: Lower Limit Of Cbf Autoregulationsupporting

confidence: 60%

Studies in Rheoencephalography (REG)

Bodó

2010

Journal of Electrical Bioimpedance

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“…However, our results together with evidence found by other research groups do suggest this is possible. From the physical point of view, it has been shown that pulsatile changes in the brain’s electrical conductivity can be observed as pulses in the electrical impedance of the head, measured by electrodes attached to the scalp surface [26, 29]. These changes in brain electrical conductivity are those observed and measured in rats by using bipolar REG with implanted electrodes [14, 15].…”

Section: Discussionmentioning

confidence: 99%

To what extent is the bipolar rheoencephalographic signal contaminated by scalp blood flow? A clinical study to quantify its extra and non-extracranial components

Pérez

2014

BioMed Eng OnLine

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BackgroundImpedance plethysmography applied to the head by using a pair of electrodes attached to the scalp surface is known as bipolar Rheoencephalography or REG I and was originally proposed to measure changes in cerebral blood volume related to the heartbeat. REG I was soon discarded in favor of other REG configurations, since most of the signal was shown to be heavily contaminated by the extracranial blood flow. The main goal of this study was to identify and compare the part of the REG I signal caused by scalp blood flow with that originating from non-extracranial sources.MethodsA clinical study involving thirty-six healthy volunteers was designed for this purpose. REG I was first registered in each subject under normal conditions. A pneumatic cuff was then placed around the head and was inflated to arrest the scalp blood flow and a second REG I was recorded. Finally, a third REG I was taken immediately after cuff deflation.ResultsThe REG I signal is attenuated, but not extinguished, during cuff inflation in a wide subject-dependent range ratio from 0.12 to 0.68 (0.37 ± 0.15). The residual REG I signal has a waveform that is markedly different from that obtained before cuff inflation, which supports the hypothesis of the intracranial origin of the residual REG I signal. Additionally, an increase of 22% in REG I amplitude was observed when the head cuff was deflated.ConclusionsWaveform differences between extra and non-extracranial components are significant and these differences could be used in a method to distinguish one from the other. However, a significant part of the REG I signal is caused by a non-extracranial source and, therefore, it should not be used as a footprint of the extracranial blood flow.

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“…Head was modeled using the conventional four-shell spherical model, which represents from inner to outer: brain, cerebrospinal fluid (CSF), skull and scalp [6], [7] (Fig. 1).…”

Section: A Modelmentioning

confidence: 99%

“…The main goal of this work is to obtain the sensitivity map of the tetrapolar REG, referred to as REG II, to cerebral electrical conductivity changes for the set of electrode arrangements used in previous works [5], [6]. For this purpose, a geometrical four-shell model of the head is used to derive the analytical solution of the sensitivity, which could be further used to inspect the influence of geometrical parameters on the solution.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of rheoencephalographic measurements to spatial brain electrical conductivity

Guijarro

Pérez

Berjano

et al. 2006

2006 International Conference of the IEEE Engineering in Medicine and Biology Society

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Rheoencephalography (REG) is impedance plethysmography applied to the head, and provides an indirect measurement of the pulsatility of the cerebral blood volume. To extend REG as a clinical and research tool, it is necessary to evaluate the sensitivity of REG measurement to local brain conductivity changes. By means of the analytical solution of a four-sphere geometrical model of the head, maps of impedance sensitivity were assessed for different electrode arrangements. Results showed a selective distribution of sensitivities, with a preference for cortical areas under electrodes. This suggests a potential for application of REG to regional evaluation of cortical cerebral perfusion.

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Influence of the scalp thickness on the intracranial contribution to rheoencephalography

Cited by 12 publications

References 26 publications

Studies in Rheoencephalography (REG)

Studies in Rheoencephalography (REG)

To what extent is the bipolar rheoencephalographic signal contaminated by scalp blood flow? A clinical study to quantify its extra and non-extracranial components

Sensitivity of rheoencephalographic measurements to spatial brain electrical conductivity

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