Accuracy of retrieving optical properties from liquid tissue phantoms using a single integrating sphere

Area of Science:

• Biomedical Optics
• Photonics
• Materials Science

Background:

• Integrating spheres (ISs) with the inverse adding-doubling (IAD) algorithm are standard for measuring optical properties of turbid media.
• Accurate optical properties (absorption and scattering coefficients) are crucial for understanding light transport in various materials.
• Previous methods often face challenges with accuracy, especially for thin, homogeneous samples.

Purpose of the Study:

• To assess the performance of a single integrating sphere system for retrieving optical properties of controlled phantom media.
• To evaluate the impact of different correction methods on the accuracy of IAD-derived optical coefficients.
• To investigate the influence of light sources and measurement parameters on the reliability of optical property determination.

Main Methods:

• Utilized a single integrating sphere system to measure total reflectance and transmittance of liquid phantoms across 500-800 nm.
• Employed two broadband light sources: a halogen lamp and a supercontinuum laser.
• Applied two correction methods: experimental sample-substitution and Monte Carlo-based corrections with IAD.

Main Results:

• Direct IAD application without corrections yielded high mean absolute errors (>0.4 cm⁻¹ for absorption, >6 cm⁻¹ for scattering).
• Correction methods significantly reduced errors, achieving 0.06-0.17 cm⁻¹ for absorption (μa) and 0.7-2 cm⁻¹ for scattering (μs').
• The choice of light source, sample geometry, signal-to-noise ratio, and correction method impacted measurement accuracy.

Conclusions:

• Correction methods are essential for accurate optical property retrieval using integrating spheres and the IAD algorithm.
• The single IS system, when properly calibrated and corrected, can reliably measure optical coefficients in turbid media.
• Understanding the interplay of measurement parameters is key to optimizing the accuracy of optical property determination.