Brainmap: The Biophysics of BOLD: Using biophysical signal modelling to advance calibrated functional MRI

Event Details

Avery Berman
PhD candidate, Biomedical Engineering, McGill University

Abstract: Calibrated functional MRI was developed to tease apart the
hemodynamic and metabolic contributions to the blood oxygenation
level-dependent (BOLD) signal using simultaneous measurements of the BOLD
signal and cerebral blood flow. While calibrated fMRI has substantially
improved our ability to image and understand aspects of brain physiology,
it has not been widely adopted due to the need for specialized gas
delivery equipment and biophysical confounds associated with the
calibration measurements. One such confound is the magnetic susceptibility
of dissolved oxygen, which, like deoxyhemoglobin, is paramagnetic. In this
talk, I will present work on modelling and measuring the susceptibility
and relaxation rates of dissolved oxygen in blood and what impact they
have on the hyperoxic BOLD signal and calibration. I will also discuss
recent efforts towards improving the accuracy of gas-free BOLD
calibration. This work could greatly increase the appeal of calibrated
fMRI by eliminating the gas challenge completely. In all, I hope these
studies underscore the role that analytical modelling and simulations can
play in improving our understanding of the biophysics of the BOLD signal
and in guiding imaging strategies to probe brain physiology.