The electrical conductivity of human cerebrospinal fluid at body temperature

Baumann, Stephen B.; Wozny, D.R.; Kelly, Shawn K.; Meno, Frank M.

doi:10.1109/10.554770

Cited by 435 publications

(299 citation statements)

References 21 publications

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“…Values commonly used in the literature are in fact the mean values across multiple references (Wagner et al, 2004). These conductivities are mostly measured at 10 Hz or higher frequencies Baumann et al, 1997;Oostendorp et al, 2000;Peters et al, 2001;Hoekema et al, 2003). To date the data for the human head measured in vivo under direct current (0 Hz) are rather scarce and date back over sixty years (Burger and Milaan, 1943;Freygang and Landau, 1955).…”

Section: Electrical Conductivity Values Of Human Tissuesmentioning

confidence: 99%

“…Modern models have compared predictions to human scalp surface recordings (Bangera et al, 2010;Datta et al, 2013), but detailed models have not been validated with intracranial recordings in vivo. Furthermore, the models depend heavily on tissue conductivity values, which have only been measured ex vivo in other animal species Baumann et al, 1997;Oostendorp et al, 2000;Peters et al, 2001;Hoekema et al, 2003). These measures differ from in vivo measurements in humans obtained over half a century ago (Burger and Milaan, 1943;Freygang and Landau, 1955).…”

Section: Introductionmentioning

confidence: 99%

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Measurements and models of electric fields in the in vivo human brain during transcranial electric stimulation

et al. 2017

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Transcranial electric stimulation aims to stimulate the brain by applying weak electrical currents at the scalp. However, the magnitude and spatial distribution of electric fields in the human brain are unknown. We measured electric potentials intracranially in ten epilepsy patients and estimated electric fields across the entire brain by leveraging calibrated current-flow models. When stimulating at 2 mA, cortical electric fields reach 0.8 V/m, the lower limit of effectiveness in animal studies. When individual whole-head anatomy is considered, the predicted electric field magnitudes correlate with the recorded values in cortical (r = 0.86) and depth (r = 0.88) electrodes. Accurate models require adjustment of tissue conductivity values reported in the literature, but accuracy is not improved when incorporating white matter anisotropy or different skull compartments. This is the first study to validate and calibrate current-flow models with in vivo intracranial recordings in humans, providing a solid foundation to target stimulation and interpret clinical trials.

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Section: Electrical Conductivity Values Of Human Tissuesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Measurements and models of electric fields in the in vivo human brain during transcranial electric stimulation

et al. 2017

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“…For example, it was reported in [18] that cerebrospinal fluid has approximately 23% higher conductivity in 37 0 C than in 25 0 C. The grey and white matters of the brain tissue have also temperature dependence, which is shown with dog brain in [19] and with rat brain in [20].…”

Section: Discussionmentioning

confidence: 99%

The conductivity of brain tissues: comparison of results in vivo and in vitro measurements

Latikka

Hyttinen

Kuurne³

et al.

2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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Abstract-Electric properties of tissues depend on many factors, including measurement frequency and temperature. Properties differ also in vivo and in vitro situations. We have collected conductivity values from several studies and compared the values measured from living tissue and tissue samples. The results show that the resistivity ratio of grey and white matter increases 36% after death, and the resistivity values increase over 100%. Keywords -Conductivity, brain tissue, source location I. INTRODUCTIONThe electric properties of tissues have a very important role in biomedical engineering. These properties determine the electrical current pathways through human body. If these properties are known, electrical models can be constructed, for example, to represent the electrical activation of the heart or the conduction of the brain activity to the scalp surface.With resistive model of the head, the information given by electroencephalography (EEG) can be effectively processed [1], [2], [3]. Models can be applied to the simulation of electric fields inside the head. For example, an electric source (dipole or set of dipoles) can be inserted inside the model and thereafter the electric field distribution can be computed. Further, the measured EEG signal can be used for obtaining the source location in the volume conductor. For example, epileptic loci can be located. In principal, accuracy of these computations is dependent on the accuracy of the volume conductor i.e. the number of compartments and their conductivities [4]. In [5] the results indicated that a 10% decrease in tissue resisitivity cause 3.0 -4.1% differences in the sensitivity distributions of the selected 3 EEG leads. In modeling the important factor is the ratio between various conductivities. The ratio of skull and brain resistivites is 15:1 rather than the commonly used ratio of 80:1 [6]. In [7] the estimated resistivity ratio of skull and brain is 14:1.There have been recent advances in source localization techniques. The amount of electrodes in EEG studies has been increased. Instead of the traditional 21 electrode 10-20 system, 64 or more electrodes are usually used. In some studies even 512 electrodes are utilized. This improves the spatial accuracy, thus giving more information about brain functions. However, most researchers continue to take conductivity parameters from standard references [8], [9]. The standard reference values are usually measured from tissue samples. An increase in tissue resistivity with time after death has been reported in [8], [10]. Literature values are also measured at much higher frequencies than EEG frequencies. II. METHODOLOGYPreviously we have made in vivo resistivity measurements with needle electrode from 9 patients with brain tumors [11]. Due to the location of tumors and selected surgical paths, it was not possible to measure both grey and white matters with every patient. The number of measurements ranged from 1 to 13 for each tissue measured.In addition to our own in vivo measurements [11], resistivity val...

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“…Table 3). [25], [26], [27] and [22]) b [26] c At 10 kHz [28] d [26] For purpose of gravity force, assumed to vary as water with temperature [29] e Assumed to be identical to water [22] f [26] Assumed to vary as water with temperature [29] g Adjusted to 20 °C [30], [23] and [26] h Stainless steel [22] The simulated lesion was assumed to consist of all grey matter or kidney tissue reaching a temperature of 60 °C or more. The lesion's volume and widest diameter perpendicular to the electrode path was then determined.…”

Section: Modelling and Simulationmentioning

confidence: 99%

Impact of cysts during radiofrequency lesioning in deep brain structures—a simulation andin vitrostudy

et al. 2007

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Radio frequency lesioning of nuclei in the thalamus or the basal ganglia can be used in order to reduce symptoms caused by e.g. movement disorders such as Parkinson's disease. Enlarged cavities containing cerebrospinal fluid (CSF) are commonly present in the basal ganglia and tend to increase in size and number with age. Since the cavities have different electrical and thermal properties compared with brain tissue, it is likely that they can affect the lesioning process and thereby the treatment outcome. Computer simulations using the Finite Element Method (FEM) and in-vitro experiments have been used to investigate the impact of cysts on lesions' size and shape. Simulations of the electric current and temperature distributions as well as convective movements have been conducted for various sizes, shapes and locations of the cysts as well as different target temperatures. Circulation of the CSF caused by the heating was found to spread heat effectively and the higher electric conductivity of the CSF increased heating of the cyst. These two effects were together able to greatly alter the resulting lesion size and shape when the cyst was in contact with the electrode tip. Similar results were obtained for the experiments.

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The electrical conductivity of human cerebrospinal fluid at body temperature

Cited by 435 publications

References 21 publications

Measurements and models of electric fields in the in vivo human brain during transcranial electric stimulation

Measurements and models of electric fields in the in vivo human brain during transcranial electric stimulation

The conductivity of brain tissues: comparison of results in vivo and in vitro measurements

Impact of cysts during radiofrequency lesioning in deep brain structures—a simulation andin vitrostudy

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