Pathlength-selective, interferometric diffuse correlation spectroscopy

Area of Science:

• Biomedical Optics
• Medical Imaging
• Optical Spectroscopy

Background:

• Diffuse Correlation Spectroscopy (DCS) non-invasively measures tissue blood flow using light scattering.
• Standard DCS has limitations in signal-to-noise ratio (SNR), depth sensitivity, and sampling rate for deep tissue measurements.
• Existing enhanced methods like time-domain DCS (TD-DCS) improve performance but may require specialized hardware.

Purpose of the Study:

• Introduce and evaluate a novel enhanced DCS method, pathlength-selective, interferometric DCS (PaLS-iDCS).
• Improve sensitivity to deep tissue hemodynamics and enhance measurement SNR.
• Provide time-of-flight (ToF) specific blood flow information without expensive time-tagging electronics.

Main Methods:

• Developed PaLS-iDCS utilizing pathlength-specific coherent gain and interferometric detection.
• Compared PaLS-iDCS against TD-DCS using Monte Carlo simulations, phantom experiments, and human subject measurements.
• Analyzed ToF distributions for blood flow and tissue optical property estimation.

Main Results:

• PaLS-iDCS demonstrated >2x SNR improvement over TD-DCS for similar ToF measurements.
• Achieved ~50% increase in sensitivity to deep tissue hemodynamics by enabling measurements at extended photon ToFs.
• PaLS-iDCS allows direct estimation of tissue optical properties from ToF distributions.

Conclusions:

• PaLS-iDCS offers a significant advancement in non-invasive blood flow monitoring.
• The method enhances SNR and deep tissue sensitivity without requiring time-resolved detection.
• PaLS-iDCS facilitates broader clinical applications of DCS technology for hemodynamics assessment.