Determination of tissue optical properties from diffuse reflectance profiles by multivariate calibration

Abstract

We describe a method for determining the reduced scattering and absorption coefficients of turbid biological media from the spatially resolved diffuse reflectance. A Sugeno Fuzzy Inference System in conjunction with data preprocessing techniques is employed to perform multivariate calibration and prediction on reflectance data generated by Monte Carlo simulations. The preprocessing consists of either a principal component analysis or a new, extended curve-fitting procedure originating from diffusion theory. Prediction tests on reflectance data with absorption coefficients between 0.04 and 0.06 mm(-1) and reduced scattering coefficients between 0.45 and 0.99 mm(-1) show the root-mean-square error of this method to be 0.25% for both coefficients. With reference to practical applications, we also describe how the prediction accuracy is affected by using relative instead of absolute reflectance data, by imposing measurement noise on the reflectance data, and by changing the number and the position of detectors.

Evaluation of Diffuse Reflectance in Multi-layered Tissue for High Intensity Laser Therapy

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“…If angle of incidence is larger than the critical angle, then the internal reflectance is set to 1. Otherwise is it is calculated by Fresnel's equation [27][28][29].…”

“…4) To determine whether or not the photon is reflected by the boundary or transmits into lower tissue, a random number (ζ), is generated. If ζ≤R (θ i) then the photon is reflected or ζ>R (θ i) then the photon is transmitted [27][28][29]. Some of the transmitted light will re-emerge through the air-skin interface into the air.…”

Chemometric analysis of frequency-domain photon migration data: quantitative measurements of optical properties and chromophore concentrations in multicomponent turbid media

“…13 In this paper, we develop a FDPM data-analysis technique based on a multivariate calibration algorithm and a set of training samples rather than on diffusion theory alone. Multivariate techniques and neural networks have previously been used to extract tissue optical properties from spatially resolved steady-state diffuse reflectance profiles [13][14][15] ; to the best of our knowledge, this is the first application of such methods to the frequency domain. Multifrequency ͑i.e., 50 -600 MHz͒, multiwavelength FDPM curves are obtained for each training sample.…”

Optical Spectroscopic Analysis of Muscle Spasticity for Low-Level Laser Therapy (LLLT)

“…Monte Carlo Simulation A Monte Carlo simulation technique, based on the statistical nature of radiation interactions, has been widely applied in laser radiation transport studies [25][26][27][28]. Monte Carlo simulation methods trace the propagation of individual photons through a turbid medium until the photon experiences complete absorption by or escape from the medium [28].…”