Spectroscopic method for determination of the absorption coefficient in brain tissue

Area of Science:

• Biomedical Optics
• Medical Physics
• Neurosurgery

Background:

• Diffuse reflectance spectroscopy (DRS) is used for real-time tissue analysis.
• Accurate quantification of chromophores in brain tissue during surgery is crucial.
• Existing models may not fully account for light transport complexities in brain tissue.

Purpose of the Study:

• To characterize a novel optical fiber probe for DRS in brain stereotactic surgery.
• To develop and validate a model for quantifying chromophore content in brain tissue.
• To improve the accuracy of absorption coefficient (μa) estimation using DRS.

Main Methods:

• Utilized Monte Carlo simulations to model light transport.
• Performed phantom measurements to validate simulation results.
• Applied a modified Beer-Lambert model to fit spectral data and quantify chromophores.

Main Results:

• Demonstrated the importance of considering light absorption for accurate optical path length (lp) calculation.
• Found that the optical path length (lp) is well-described by the equation: lp=a+b ln(Is)+c ln(μa)+d ln(Is)ln(μa).
• Identified reflected light intensity for scattering alone (Is) as a key parameter.

Conclusions:

• The developed model improves the estimation of absorption coefficients (μa) in brain tissue.
• Accurate characterization of optical path length (lp) is essential for reliable chromophore quantification.
• The derived equation provides a framework for similar optical probes used in neurosurgery.