The dynamics of cerebrovascular reactivity shown with transfer function analysis

Area of Science:

• Neuroimaging
• Physiology
• Medical Engineering

Background:

• Cerebrovascular reactivity (CVR) assesses cerebrovasculature health by measuring cerebral blood flow (CBF) changes in response to carbon dioxide (CO2).
• Blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) provides CVR maps, showing response magnitude but not the time course (speed).

Purpose of the Study:

• To introduce transfer function analysis (TFA) for BOLD signal response to CO2.
• To evaluate TFA's ability to provide dynamic CVR information, including response speed and fidelity.

Main Methods:

• Transfer function analysis (TFA) applied to BOLD MRI data during CO2 challenge.
• Calculation of gain (magnitude), phase (speed), and coherence (fidelity) of the cerebrovascular response.

Main Results:

• TFA yields maps of gain, phase, and coherence, complementing traditional CVR magnitude maps.
• Phase and coherence maps offer insights into the temporal dynamics of the cerebrovascular response.

Conclusions:

• TFA enhances cerebrovascular assessment by revealing the dynamics of CBF control and distribution.
• Dynamic CVR information from TFA may improve understanding of cerebrovascular pathophysiology in various conditions.