High-speed swept source optical coherence Doppler tomography for deep brain microvascular imaging.

Area of Science:

• Neuroimaging
• Biomedical Optics
• Vascular Biology

Background:

• Noninvasive microvascular imaging is crucial for brain studies.
• Existing optical coherence Doppler tomography (ODT) faces limitations in high-speed deep brain imaging.
• Advancing imaging techniques is essential for understanding brain microcirculation.

Purpose of the Study:

• To develop and validate a high-speed swept-source ODT (SS-ODT) system for deep brain microvascular imaging.
• To overcome limitations of phase errors and enhance flow sensitivity in ODT.
• To demonstrate the capability of SS-ODT for dynamic cerebral blood flow (CBF) monitoring in vivo.

Main Methods:

• A 1.3 μm SS-ODT system utilizing a 200 kHz vertical-cavity-surface-emitting laser was engineered.
• Spectral phase encoding and instantaneous correlation were employed to mitigate phase errors.
• Phantom studies assessed flow sensitivity, followed by in vivo imaging of mouse brains through thinned skulls.

Main Results:

• The SS-ODT system achieved a minimally detectable flow sensitivity of 268.2 μm/s in phantoms.
• In vivo imaging revealed 3D CBF networks over a large field-of-view (8.5 × 5 × 3.2 mm³).
• Flows from 0.3 mm/s to 3 cm/s were detected at depths up to 3.2 mm, capturing dynamic changes induced by cocaine and ischemic events.

Conclusions:

• The developed high-speed SS-ODT system significantly advances noninvasive deep brain microvascular imaging capabilities.
• It offers high flow sensitivity, a large field-of-view, and fast imaging speeds, suitable for functional brain studies.
• This technology holds promise for monitoring complex CBF dynamics and neurological conditions in real-time.