Time-domain diffuse correlation spectroscopy at large source detector separation for cerebral blood flow recovery

Area of Science:

• Biomedical Optics
• Physiological Measurement
• Medical Imaging

Background:

• Time-domain diffuse correlation spectroscopy (td-DCS) measures blood flow by analyzing photon time-of-flight (TOF) distributions.
• Accurate blood flow recovery in td-DCS is influenced by instrument response function (IRF), TOF gating, and source-detector separation (SDS).

Purpose of the Study:

• To evaluate the performance of td-DCS for cerebral blood flow (CBF) recovery at varying SDSs (1.5, 2, and 2.5 cm).
• To optimize TOF gating parameters and assess SDS sensitivity for superficial and deep tissue layers.

Main Methods:

• Phantom experiments were conducted to characterize the td-DCS system.
• Quality metrics (coefficient of variation, contrast-to-noise ratios) identified optimal TOF gates.
• Sensitivity metrics evaluated SDS performance for different tissue depths.
• td-DCS was tested on healthy volunteers during physiological challenges (cuff occlusion, breathing tasks).

Main Results:

• Phantom studies demonstrated that increasing SDS from 1.5 cm to 2.5 cm more than doubles sensitivity for estimating perfusion in a 1.5 cm deep tissue layer.
• Optimal TOF gates were identified for extracting particle dynamics.

Conclusions:

• td-DCS performance in blood flow recovery is significantly affected by SDS.
• Increased SDS enhances the ability of td-DCS to probe deeper tissue layers, improving CBF estimation accuracy.