Radiance backscattered by a strongly scattering medium in the high spatial frequency limit

Area of Science:

• Optics
• Radiative Transfer Theory
• Biomedical Imaging

Background:

• Radiative transfer describes light interaction with scattering and absorbing media.
• Spatial frequency domain imaging (SFDI) is an emerging technique for optical property measurement.

Purpose of the Study:

• To investigate the behavior of light backscattered from a scattering medium under specific spatial frequency conditions.
• To establish a theoretical basis for using SFDI to measure optical properties, specifically the phase function.

Main Methods:

• Theoretical analysis of radiative transfer equation for a spatially modulated plane wave.
• Approximation for high spatial frequencies relative to the scattering coefficient.
• Numerical simulations using the discrete ordinate method and source integration interpolation method.

Main Results:

• First-order scattering dominates backscattered radiance at high spatial frequencies.
• Backscattered radiance concentrates along a specific curve on the backscattered hemisphere.
• The radiance along this curve is directly proportional to the phase function.

Conclusions:

• The derived results are intrinsic to the radiative transfer equation at high spatial frequencies.
• This provides a direct method for spatial frequency domain imaging to measure the sample's phase function.
• Numerical simulations validate the theoretical findings.