Thomas W. Okell

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Functional magnetic resonance imaging typically measures signal increases arising from changes in the transverse relaxation rate over small regions of the brain and associates these with local changes in cerebral blood flow, blood volume and oxygen metabolism. Recent developments in pulse sequences and image analysis methods have improved the specificity of(More)
Several brain regions have been implicated in human painful experiences, but none have been proven to be specific to pain. We exploited arterial spin-labeling quantitative perfusion imaging and a newly developed procedure to identify a specific role for the dorsal posterior insula (dpIns) in pain. Tract tracing studies in animals identify a similar region(More)
Medical imaging has enormous potential for early disease prediction, but is impeded by the difficulty and expense of acquiring data sets before symptom onset. UK Biobank aims to address this problem directly by acquiring high-quality, consistently acquired imaging data from 100,000 predominantly healthy participants, with health outcomes being tracked over(More)
A new noninvasive MRI method for vessel-selective angiography is presented. The technique combines vessel-encoded pseudocontinuous arterial spin labeling with a two-dimensional dynamic angiographic readout and was used to image the cerebral arteries in healthy volunteers. Time-of-flight angiograms were also acquired prior to vessel-selective dynamic(More)
The original concept of the ischaemic penumbra suggested imaging of regional cerebral blood flow and metabolism would be required to identify tissue that may benefit from intervention. Amide proton transfer magnetic resonance imaging, a chemical exchange saturation transfer technique, has been used to derive cerebral intracellular pH in preclinical stroke(More)
Until recently, no direct comparison between [(15)O]water positron emission tomography (PET) and arterial spin labeling (ASL) for measuring cerebral blood flow (CBF) was possible. With the introduction of integrated, hybrid magnetic resonance (MR)-PET scanners, such a comparison becomes feasible. This study presents results of CBF measurements recorded(More)
When the primary visual cortex (V1) is damaged, there are a number of alternative pathways that can carry visual information from the eyes to extrastriate visual areas. Damage to the visual cortex from trauma or infarct is often unilateral, extensive and includes gray matter and white matter tracts, which can disrupt other routes to residual visual(More)
Arterial spin labeling (ASL) sequences that incorporate multiple postlabeling delay (PLD) times allow estimation of when arterial blood signal arrives within a region of interest. Sequences that account for such variability may improve the reliability of ASL and therefore make the technique well suited for future clinical and experimental investigations of(More)
Arterial Spin Labeling (ASL) permits the non-invasive assessment of cerebral perfusion, by magnetically labeling all the blood flowing into the brain. Vessel encoded (VE) ASL extends this concept by introducing spatial modulations of the labeling procedure, resulting in different patterns of label applied to the blood from different vessels. Here a Bayesian(More)
PURPOSE Vessel-encoded (VE) pseudo-continuous arterial spin labeling (p-CASL) is a territorial ASL (T-ASL) technique to identify the perfusion territories of cerebral arteries. The aim of this study was to validate the output of three Vessel-encoded p-CASL image processing methods, k-means clustering with and without subsequent linear analysis and a(More)