Dynamic speckle, reduced extinction, and multiple scattering in holographic optical coherence imaging

Area of Science:

• Biomedical Optics
• Optical Imaging
• Light Scattering

Background:

• Holographic optical coherence imaging (HOCI) captures depth-resolved complex fields.
• Temporal speckle in HOCI is a valuable but path-mixed observable.
• Understanding light propagation is crucial for interpreting HOCI data in scattering media.

Purpose of the Study:

• To develop an operational HOCI framework linking scattering properties to imaging parameters.
• To establish criteria for interpreting HOCI dynamics in optically dense samples.
• To determine practical depth ranges for HOCI analysis.

Main Methods:

• Developed an HOCI framework to measure bead-phantom attenuation and reflectivity.
• Utilized reduced-extinction and transport-mean-free-path estimates.
• Investigated size-varied bead suspensions (0.05 µm and 0.50 µm) to assess path mixing.

Main Results:

• Established a link between tumor-spheroid fluctuation descriptors and phantom measurements.
• Identified conditions where coherence-gated profiles deviate from single-scattering behavior.
• 0.50 µm beads exhibited significant path mixing, while 0.05 µm beads remained near the single-scattering limit.

Conclusions:

• Defined practical depth ranges and fitting criteria for HOCI in optically dense samples.
• Provided a framework for interpreting HOCI dynamics based on scattering properties.
• Demonstrated the influence of bead size on light path mixing in HOCI.