Using saturation bands to null signal from inflowing blood in single-slice fMRI: Toward a rapidly sampled black-blood functional contrast

Synopsis

Keywords: fMRI Acquisition, New Signal Preparation Schemes, Acquisition Methods, Blood Vessels, Brain, Contrast Mechanisms, fMRI (task based), fMRI Acquisition, New Signal Preparation Schemes, Novel Contrast Mechanisms, Pulse Sequence Design, RF Pulse Design & Fields, Vascular, Velocity & Flow, inflow, black-blood contrast, blood nulling, functional contrast, blood flow, blood volume, arteries, veins, flow related signal enhancement

Motivation: Magnetization-preparation schemes using inversion recovery measure aspects of hemodynamics like perfusion and blood volume, but their temporal resolution is limited by physiology, i.e., long blood arrival/transit times.

Goal(s): To study brain hemodynamics at high temporal resolutions with novel inflow saturation.

Approach: We applied saturation bands on both sides of a rapidly-sampled single imaging slice to suppress inflow-related signal and produce black-blood functional contrast sensitive to macrovascular blood volume.

Results: Phantom experiments show successful suppression of inflow signal with flow-velocity-dependence at low- and high-velocity regimes but independence at mid-regime. Human brain vessels exhibited partial signal suppression, with more functional suppression seen in larger vessels.

Impact: Fast blood nulling may be achievable using local saturation bands contiguous to an imaging slice rather than a global inversion slab, enabling functional contrasts sensitive to macrovascular blood flow-velocity and volume suitable for studying fast hemodynamics in specific vascular compartments.