title: Bayesian inference of hemodynamic changes in functional arterial spin labeling data.
abstract: The study of brain function using MRI relies on acquisition techniques that are sensitive to different aspects of the hemodynamic response contiguous to areas of neuronal activity. For this purpose different contrasts such as arterial spin labeling (ASL) and blood oxygenation level dependent (BOLD) functional MRI techniques have been developed to investigate cerebral blood flow (CBF) and blood oxygenation, respectively. Analysis of such data typically proceeds by separate, linear modeling of the appropriate CBF or BOLD time courses. In this work an approach is developed that provides simultaneous inference on hemodynamic changes via a nonlinear physiological model of ASL data acquired at multiple echo times. Importantly, this includes a significant contribution by changes in the static magnetization, M, to the ASL signal. Inference is carried out in a Bayesian framework. This is able to extract, from dual-echo ASL data, probabilistic estimates of percentage changes of CBF, R(2) (*), and the static magnetization, M. This approach provides increased sensitivity in inferring CBF changes and reduced contamination in inferring BOLD changes when compared with general linear model approaches on single-echo ASL data. We also consider how the static magnetization, M, might be related to changes in CBV by assuming the same mechanism for water exchange as in vascular space occupancy.
authors.affiliation: University of Oxford, Centre for Functional MRI of the Brain, John Radcliffe Hospital, Oxford, United Kingdom. woolrich@fmrib.ox.ac.uk
authors.forename: Mark W
authors.initials: MW
authors.lastname: Woolrich
authors.forename: Peter
authors.initials: P
authors.lastname: Chiarelli
authors.forename: Daniel
authors.initials: D
authors.lastname: Gallichan
authors.forename: Joanna
authors.initials: J
authors.lastname: Perthen
authors.forename: Thomas T
authors.initials: TT
authors.lastname: Liu
mesh_terms: D001499:Bayes Theorem; D001783:Blood Flow Velocity / Q000502:physiology; D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010100:Oxygen / Q000097:blood; D013113:Spin Labels; D014793:Visual Cortex / Q000502:physiology*
chemical_list: D013113:Spin Labels; D010100:Oxygen