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Development of a portable multi-channel broadband near infrared spectroscopy instrument to measure brain tissue oxygenation and metabolism during functional activation and seizures

de Roever, Janet Isabel; (2019) Development of a portable multi-channel broadband near infrared spectroscopy instrument to measure brain tissue oxygenation and metabolism during functional activation and seizures. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Epilepsy is a common neurological disorder often developed during childhood, characterised by abnormal neuronal discharges. These spontaneous recurrent seizures can be associated with poor long-term neurological development. Near-infrared spectroscopy (NIRS) is a non-invasive tech- nique able to monitor cerebral concentration changes in oxygenated- (∆[HbO2]) and deoxygenated- (∆[HHb]) haemoglobin. However, current commercial NIRS systems use only a few wavelengths, limiting their use to haemodynamic monitoring. Broadband NIRS (bNIRS) systems use a larger number of wavelengths enabling changes in concentration of the oxidation state of cytochrome-c- oxidase (∆[oxCCO]) to be determined, a marker of cellular metabolism. This thesis describes the development and miniaturisation of an existing bNIRS system to monitor haemodynamic and metabolic changes in children with epilepsy. Using the latest technological advancements, the bulk and complexity of the system was reduced while increasing the number of measurement channels. Two miniature tungsten halogen light sources were utilised with time- multiplexing capabilities implemented (0.5Hz). Bifurcated optical fibre bundles (2.8mm diameter) connected to each light source and twelve detector fibre bundles (1mm diameter) arranged linearly into a ferrule (25mm diameter); modification of the interface between the detectors and lens-based spectrograph ensured compatibility with the increased detector number. Light was collimated to a diffraction grating with a wider 308nm bandwidth and the largest CCD image sensor available (1340x1300 array, 26.8x26mm) was integrated into the system. LabVIEW software was updated to enable simultaneous, real-time collection and display of intensity and concentration changes. Extensive testing of the system was performed; in-vivo testing in healthy adults using a Stroop task demonstrated a typical haemodynamic response with regional variation in metabolism. Si- multaneous bNIRS and electroencephalography data were collected from 12 children with epilepsy in the Neurology Unit. One patient case study is presented in detail, with temporal data from 17 seizures collected. A large decrease in metabolism was observed in the left posterior region, corresponding to a region of cortical malformation, suggesting an energetic deficiency in this re- gion. This indicates the potential for ∆[oxCCO] as an investigative marker in monitoring seizures, providing localised information about cellular oxygen utilisation.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Development of a portable multi-channel broadband near infrared spectroscopy instrument to measure brain tissue oxygenation and metabolism during functional activation and seizures
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10088354
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