Signal attenuation and localization in optical coherence tomography studied by Monte Carlo simulation

Area of Science:

• Biomedical Optics
• Medical Imaging
• Computational Physics

Background:

• Optical Coherence Tomography (OCT) is a crucial imaging modality.
• Understanding light-tissue interaction is vital for OCT accuracy.
• Monte Carlo simulations offer a robust method for modeling photon transport.

Purpose of the Study:

• To develop and validate a Monte Carlo model for OCT simulations.
• To investigate the impact of scattering properties on OCT imaging depth.
• To assess the accuracy of OCT in different scattering media.

Main Methods:

• Combined geometrical optics OCT probe model with 3D Monte Carlo photon propagation.
• Simulated photon propagation in homogeneous media mimicking intralipid and blood.
• Analyzed detected backscattered photons based on optical depth and scattering anisotropy (g).

Main Results:

• OCT accurately detected minimally scattered photons within <3 mean free paths (mfp) in intralipid.
• Deeper imaging in intralipid showed loss of backscattering localization due to stray photons.
• In simulated blood (highly anisotropic scattering), OCT accuracy was maintained to >40 mfp, with good correlation to probe focus.

Conclusions:

• OCT is effective for imaging superficial structures (<3 mfp) in moderately scattering tissues.
• Highly forward-scattering media like blood allow for deeper OCT penetration (>40 mfp) with accurate localization.
• The developed Monte Carlo model provides insights into OCT's depth limitations and capabilities.