Measurement of canine cerebral oedema using vector impedance methods

Kao, Hua-Lin; Shwedyk, E.; Cardoso, Érico R.

doi:10.1080/01616412.1991.11739998

Cited by 3 publications

(3 citation statements)

References 10 publications

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“…Magnetic brain monitoring could, in fact, provide a useful method, as there exists still no noninvasive and continuous instrumentation for the detection of brain edema. This application relies on the fact that water accumulations in tissue cause local changes of the PEP and , as has been demonstrated with invasive measurements, e.g., in [11] and [12].…”

Section: B Example 1: Brain Edema Monitoringmentioning

confidence: 99%

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Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations

Scharfetter

Casañas

Rosell

2003

IEEE Trans. Biomed. Eng.

120

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Abstract-Magnetic induction spectroscopy (MIS) aims at the contactless measurement of the passive electrical properties (PEP), , and of biological tissues via magnetic fields at multiple frequencies. Whereas previous publications focus on either the conductive or the magnetic aspect of inductive measurements, this article provides a synthesis of both concepts by discussing two different applications with the same measurement system: 1) monitoring of brain edema and 2) the estimation of hepatic iron stores in certain pathologies. We derived the equations to estimate the sensitivity of MIS as a function of the PEP of biological objects. The system requirements and possible systematic errors are analyzed for a MIS-channel using a planar gradiometer (PGRAD) as detector. We studied 4 important error sources: 1) moving conductors near the PGRAD; 2) thermal drifts of the PGRAD-parameters; 3) lateral displacements of the PGRAD; and 4) phase drifts in the receiver. All errors were compared with the desirable resolution. All errors affect the detected imaginary part (mainly related to ) of the measured complex field much less than the real part (mainly related to and ). Hence, the presented technique renders possible the resolution of (patho-) physiological changes of the electrical conductivity when applying highly resolving hardware and elaborate signal processing. Changes of the magnetic permeability and permittivity in biological tissues are more complicated to deal with and may require chopping techniques, e.g., periodic movement of the object.Index Terms-Brain edema, impedance spectroscopy, iron overload, magnetic induction tomograpy, passive electrical properties of tissue.

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Section: B Example 1: Brain Edema Monitoringmentioning

confidence: 99%

“…A spurious change can be calculated according to (11) In terms of the model parameters, can be expressed as (12) Decomposition into real and imaginary part gives (13) The calculation of the partial derivatives and of (13) was carried out automatically with the symbolic toolbox of MATLAB.…”

Section: B Thermal Mismatch Of the Gradiometer Coilsmentioning

confidence: 99%

Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations

Scharfetter

Casañas

Rosell

2003

IEEE Trans. Biomed. Eng.

120

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“…MIT is a non-invasive and contactless imaging method for reconstructing the changes κ of the complex conductivity distribution κ = σ + jω in a target object (Griffiths 2001, Griffiths et al 1999, Korjenevsky and Cherepenin 1999, Korjenevsky et al 2000, Peyton et al 1995. Magnetically coupled conductivity sensors (Netz et al 1993), specifically when applied at multiple frequencies (Scharfetter et al 2003), appear especially attractive for the monitoring of pathologies in the brain, which are correlated with local fluid shifts, e.g., oedema (Kao et al 1991), haemorrhages or epileptic events. To this end, a sinusoidal time varying magnetic field B 0 generated by an excitation coil penetrates the object under investigation.…”

Section: Introductionmentioning

confidence: 99%

Detection of brain oedema using magnetic induction tomography: a feasibility study of the likely sensitivity and detectability

Merwa¹,

Hollaus²,

Bíró³

et al. 2004

Physiol. Meas.

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The detection and continuous monitoring of brain oedema is of particular interest in clinical applications because existing methods (invasive measurement of the intracranial pressure) may cause considerable distress for the patients. A new non-invasive method for continuous monitoring of an oedema promises the use of multi-frequency magnetic induction tomography (MIT). MIT is an imaging method for reconstructing the changes of the conductivity deltakappa in a target object. The sensitivity of a single MIT-channel to a spherical oedematous region was analysed with a realistic model of the human brain. The model considers the cerebrospinal fluid around the brain, the grey matter, the white matter, the ventricle system and an oedema (spherical perturbation). Sensitivity maps were generated for different sizes and positions of the oedema when using a coaxial coil system. The maps show minimum sensitivity along the coil axis, and increasing values when moving the perturbation towards the brain surface. Parallel to the coil axis, however, the sensitivity does not vary significantly. When assuming a standard deviation of 10(-7) for the relative voltage change due to the system's noise, a centrally placed oedema with a conductivity contrast of 2 with respect to the background and a radius of 20 mm can be detected at 100 kHz. At higher frequencies the sensitivity increases considerably, thus suggesting the capability of multi-frequency MIT to detect cerebral oedema.

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A Square Signal Wave Method for Measurement of Brain Extra- and Intracellular Water Content

et al. 1994

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Measurement of canine cerebral oedema using vector impedance methods

Cited by 3 publications

References 10 publications

Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations

Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations

Detection of brain oedema using magnetic induction tomography: a feasibility study of the likely sensitivity and detectability

A Square Signal Wave Method for Measurement of Brain Extra- and Intracellular Water Content

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