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Measurement of Electrical Current Density Distribution within the tissues of the head by Magnetic Resonance Imaging

Gamba, Humberto Remigio; (1996) Measurement of Electrical Current Density Distribution within the tissues of the head by Magnetic Resonance Imaging. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

in vivo and in vitro images of the distribution of electrical current inside the head of newborn piglets that arise from electrodes placed on the top of the head and in the root of the mouth are presented in this thesis. The images are obtained from the magnetic field induced by the electrical current propagating inside the head which is measured using nuclear magnetic resonance (NMR) phase images. From the phase images the electrical current images are then calculated using Ampere's law. Following a review of the NMR principles, the technique of measuring electrical current by NMR is described in detail. The implementation of the technique was then validated with both numerical simulations and experiments with a cylindrical and a cubical phantom. The sources of noise in the NMR data are also reviewed and their effect in the calculated current images is analysed both theoretically and experimentally using the phantoms. From the current images, preferential paths used by the electrical current in passing from the electrode under the neck to the electrode on the top of the head could be identified. The total current per region in the head is determined by segmenting the NMR intensity image and integrating the current through each region. Remarkable differences in the current distribution between the in vivo and post mortem experiment were found. The piglet head inclination during the in vivo experiment was also found to affect the current orientation. It was thought that this effect might be related to a shift in blood volume or flow when the head is inclined, and some evidence for such a change in blood volume, measured using near infrared spectroscopy is presented.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Measurement of Electrical Current Density Distribution within the tissues of the head by Magnetic Resonance Imaging
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Applied sciences; Electrical current; Nuclear magnetic resonance
URI: https://discovery.ucl.ac.uk/id/eprint/10098793
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