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The BOLD MRI response of the brain to alterations in arterial blood pressure

The BOLD MRI response of the brain to alterations in arterial blood pressure
The BOLD MRI response of the brain to alterations in arterial blood pressure
The impact of blood pressure changes on cerebral blood flow is an important area of investigation. The cerebral autoregulation mechanism acts to maintain blood supply to the brain, despite changes in blood pressure. Blood flow alterations are closely linked to neuronal activation, and this activity can be visualised using blood oxygenation level dependent magnetic resonance imaging (BOLD MRI) – functional MRI. The aim of this project is to investigate the effect of dynamic blood pressure stimuli on the BOLD MRI signal in the brain. Two blood pressure stimuli were employed; thigh cuff deflation and the Valsalva manoeuvre. BOLD MRI signal changes were measured throughout both challenges. Arterial and venous blood pressure and tympanic membrane displacement (TMD) measurements were also made during these challenges. Blood pressure data was used to drive two linked models. The first model represented cerebral vascular physiology (Ursino) and this fed into a second model (Buxton), which predicted the resulting BOLD signal changes. This allowed comparison with experimental BOLD data. TMD data was also compared to intracranial pressure changes predicted by the Ursino model. The experimental BOLD data was found to agree reasonably well with the BOLD signal changes predicted by the modelling. BOLD signal changes are most influenced by deoxyhaemoglobin changes, predominantly as a result of blood flow alterations during the blood pressure challenges, which are not immediately compensated for by the autoregulation mechanism. TMD changes did not reflect intracranial pressure changes predicted by the modelling. In conclusion, if such blood pressure changes do occur during a functional MRI experiment, they may cause changes in the BOLD signal that are not due to neuronal activation. These signal changes may be employed to investigate the cerebral autoregulation mechanism across the brain, or to correct for inaccuracies in functional MRI data in patients with impaired cerebral autoregulation
Darekar, Angela Anagha
314a85df-6c85-43e1-8312-9b7616a54cc7
Darekar, Angela Anagha
314a85df-6c85-43e1-8312-9b7616a54cc7
Fleming, John S.
9a23102d-6740-430a-ac74-89938b328ec3

Darekar, Angela Anagha (2009) The BOLD MRI response of the brain to alterations in arterial blood pressure. University of Southampton, School of Medicine, Doctoral Thesis, 284pp.

Record type: Thesis (Doctoral)

Abstract

The impact of blood pressure changes on cerebral blood flow is an important area of investigation. The cerebral autoregulation mechanism acts to maintain blood supply to the brain, despite changes in blood pressure. Blood flow alterations are closely linked to neuronal activation, and this activity can be visualised using blood oxygenation level dependent magnetic resonance imaging (BOLD MRI) – functional MRI. The aim of this project is to investigate the effect of dynamic blood pressure stimuli on the BOLD MRI signal in the brain. Two blood pressure stimuli were employed; thigh cuff deflation and the Valsalva manoeuvre. BOLD MRI signal changes were measured throughout both challenges. Arterial and venous blood pressure and tympanic membrane displacement (TMD) measurements were also made during these challenges. Blood pressure data was used to drive two linked models. The first model represented cerebral vascular physiology (Ursino) and this fed into a second model (Buxton), which predicted the resulting BOLD signal changes. This allowed comparison with experimental BOLD data. TMD data was also compared to intracranial pressure changes predicted by the Ursino model. The experimental BOLD data was found to agree reasonably well with the BOLD signal changes predicted by the modelling. BOLD signal changes are most influenced by deoxyhaemoglobin changes, predominantly as a result of blood flow alterations during the blood pressure challenges, which are not immediately compensated for by the autoregulation mechanism. TMD changes did not reflect intracranial pressure changes predicted by the modelling. In conclusion, if such blood pressure changes do occur during a functional MRI experiment, they may cause changes in the BOLD signal that are not due to neuronal activation. These signal changes may be employed to investigate the cerebral autoregulation mechanism across the brain, or to correct for inaccuracies in functional MRI data in patients with impaired cerebral autoregulation

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Submitted date: September 2009
Organisations: University of Southampton, Faculty of Medicine

Identifiers

Local EPrints ID: 196567
URI: https://eprints.soton.ac.uk/id/eprint/196567
PURE UUID: 7e2c6a99-4ec3-4cb0-8ae2-d9ac423f6a7f

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Date deposited: 09 Sep 2011 08:14
Last modified: 18 Jul 2017 11:22

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Contributors

Author: Angela Anagha Darekar
Thesis advisor: John S. Fleming

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