Characterizing dynamic cerebral vascular reactivity using a hybrid system combining time-resolved near-infrared and...

Area of Science:

• Neuroscience
• Biomedical Optics
• Physiology

Background:

• Cerebrovascular reactivity (CVR) is crucial for maintaining brain health.
• Accurate characterization of CVR requires distinguishing brain signals from superficial scalp hemodynamics.
• Optical techniques like NIRS and DCS offer non-invasive methods to assess CVR.

Purpose of the Study:

• To characterize dynamic cerebrovascular reactivity (CVR) in healthy adults.
• To evaluate a hybrid optical system combining time-resolved (TR) near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) for CVR assessment.
• To investigate the impact of scalp hemodynamics on CVR measurements and methods to mitigate it.

Main Methods:

• Utilized a hybrid optical system integrating TR-NIRS and DCS.
• Recorded blood flow and oxygenation responses to a hypercapnic challenge.
• Acquired data at varying source-detector separations (rSD) and applied moment analysis to TR-NIRS data.

Main Results:

• Scalp contamination significantly distorted CVR time courses, especially for oxyhemoglobin, at shorter rSD.
• TR-NIRS depth sensitivity and DCS's focus on blood flow effectively reduced scalp signal interference.
• Blood flow and oxygenation exhibited similar reactivity speeds in healthy individuals.

Conclusions:

• The hybrid TR-NIRS/DCS system accurately characterizes dynamic CVR by minimizing scalp artifacts.
• This non-invasive, portable approach is suitable for studying altered CBF-oxygenation relationships in aging and cerebrovascular diseases.