A biophysical model of blood flow and water exchange in the brain with applications to MRI imaging

• Applicant: Grant Hartung, Ph.D.
• Subject Area: Mechanics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 543670971

Magnetic resonance imaging (MRI) remains one of the primary methods for observing brain and hemodynamic health in humans. Thus, MRI has the potential to uncover hemodynamic biomarkers preceding more severe symptoms such as behavioral, motor, or personality changes and improve preventative medicine towards age-related cognitive disfunction. Unfortunately, the current tools for imaging hemodynamic health cannot differentiate between changes in function (e.g. blood flow) and structure (e.g. blood volume). As these two categories present different and independent artifacts in potential biomarkers, untangling their contributions to the MRI signal is essential for early biomarker identification and use. So here we propose to build a framework to compute MRI signals from intra-vascular contrast. We aim to calculate an MRI signal and investigate the contribution from individual blood vessels. We will extend a simulation platform that uses 3-dimensional vascular anatomy (VAN) models coupled to biophysical equations of blood flow during baseline and with changes accompanying neural activation. We will extend these simulations to include water exchange with the surrounding brain tissue which accounts for in-vivo mixing of contrasts between these two compartments (blood and tissue) with different magnetic properties. We will then create the first stochastic simulation of proton movement in an MRI magnetic field while traversing the blood stream, exchanging with the tissue, and movement through the tissue, culminating in a predicted MRI signal. We will then develop applications to the VAscular Space Occupancy (VASO) and functional Arterial Spin Labeling (fASL) sequences to help describe the biophysical relationships underlying these signals.

• DFG Programme: WBP Position