Bottom layer absorption coefficients extraction from two-layer phantoms based on crossover point in diffuse...

Area of Science:

• Biomedical Optics
• Optical Imaging
• Spectroscopy

Background:

• Existing optical imaging and spectroscopy techniques often lack information on penetration depth in multilayered tissues.
• A need exists for simple, safe, and applicable diagnostic methods to probe deeper tissue layers.

Purpose of the Study:

• To develop and validate a fiber-based diffuse reflectance (DR) technique for quantifying optical properties in deep, hidden tissue layers.
• To determine the absorption coefficients of a bottom layer in a two-layer (2L) phantom system.

Main Methods:

• Utilized a fiber-based DR experiment with varying fiber core diameters to study optical properties at greater penetration depths.
• Employed two-layer (2L) tissue-mimicking solid phantoms with distinct top and bottom layer optical properties.
• Identified a unique crossover point (Cp) in the DR intensity profile, analyzing slopes before and after the Cp to differentiate layer properties.

Main Results:

• The DR technique successfully extracted absorption coefficients of the bottom layer in 2L phantoms, showing good agreement with known values.
• Distinct slopes before and after the crossover point (Cp) indicated differences in optical properties between the top and bottom layers.
• The method accurately determined the position of the Cp even with varying concentrations of Indian black ink in the hidden layer.

Conclusions:

• The crossover point (Cp) in DR profiles is dependent on the absorption coefficients and thickness of both layers in a 2L structure.
• The DR technique allows for the determination of either the top layer thickness or absorption coefficients, given the other parameters.
• Analyzing the slope before the Cp in the DR profile enables the characterization of bottom layer absorption properties, avoiding averaged behavior.