Method to improve the depth sensitivity of diffuse reflectance measurements to absorption changes in optically turbid...

Area of Science:

• Biomedical Optics
• Medical Physics
• Optical Imaging

Background:

• Time-resolved near-infrared diffuse reflectance measurement is crucial for assessing brain oxygenation and perfusion.
• Current methods face challenges in discriminating deep intracerebral absorption changes.
• Understanding sensitivity distributions is key to improving spatial resolution.

Purpose of the Study:

• To simulate and analyze spatial sensitivity distributions for time-resolved near-infrared diffuse reflectance measurements.
• To investigate how different source-detector separations and optical properties affect sensitivity.
• To propose a novel measurement geometry for enhanced discrimination of deep brain optical signals.

Main Methods:

• Simulated sensitivity factors using the diffusion equation solution.
• Calculated sensitivity distributions for statistical moments of time-resolved photon distributions (DTOFs), including mean time of flight and variance.
• Investigated differential sensitivity for varying source-detector separations and proposed a dual-source, dual-detector geometry.

Main Results:

• Generated sensitivity distributions for various parameters and source-detector separations.
• Demonstrated positive sensitivity in deep brain compartments located between detection spots.
• Observed negative and smaller amplitude sensitivity in superficial compartments.

Conclusions:

• The proposed dual-source, dual-detector geometry with differential signal analysis enhances sensitivity in deep brain regions.
• This technique improves the discrimination of intracerebral absorption changes.
• It offers a promising advancement for near-infrared spectroscopy (NIRS) applications in brain oxygenation and perfusion monitoring.