Implementation of the extended Kalman filter for determining the optical and geometrical properties of turbid layered media by time-resolved single distance measurements

Baez, Guido Rodrigo; García, Héctor; Grosenick, Dirk; Wabnitz, Heidrun

doi:10.1364/boe.11.000251

Cited by 4 publications

(6 citation statements)

References 26 publications

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“…These results are comparable to the results of similar experiments that were reported in e.g. [ 33 , 36 , 43 ]. Possible drifts in the laser output could affect the moments, which may account for the slight deviations from a horizontal line for the determined µ a,Deep in Exp.…”

Section: Resultssupporting

confidence: 92%

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Two-layered blood-lipid phantom and method to determine absorption and oxygenation employing changes in moments of DTOFs

Sudakou¹,

Wabnitz

Liemert

et al. 2023

Biomed. Opt. Express

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Near-infrared spectroscopy (NIRS) is an established technique for measuring tissue oxygen saturation (StO2), which is of high clinical value. For tissues that have layered structures, it is challenging but clinically relevant to obtain StO2 of the different layers, e.g. brain and scalp. For this aim, we present a new method of data analysis for time-domain NIRS (TD-NIRS) and a new two-layered blood-lipid phantom. The new analysis method enables accurate determination of even large changes of the absorption coefficient (Δµa) in multiple layers. By adding Δµa to the baseline µa, this method provides absolute µa and hence StO2 in multiple layers. The method utilizes (i) changes in statistical moments of the distributions of times of flight of photons (DTOFs), (ii) an analytical solution of the diffusion equation for an N-layered medium, (iii) and the Levenberg–Marquardt algorithm (LMA) to determine Δµa in multiple layers from the changes in moments. The method is suitable for NIRS tissue oximetry (relying on µa) as well as functional NIRS (fNIRS) applications (relying on Δµa). Experiments were conducted on a new phantom, which enabled us to simulate dynamic StO2 changes in two layers for the first time. Two separate compartments, which mimic superficial and deep layers, hold blood-lipid mixtures that can be deoxygenated (using yeast) and oxygenated (by bubbling oxygen) independently. Simultaneous NIRS measurements can be performed on the two-layered medium (variable superficial layer thickness, L), the deep (homogeneous), and/or the superficial (homogeneous). In two experiments involving ink, we increased the nominal µa in one of two compartments from 0.05 to 0.25 cm−1, L set to 14.5 mm. In three experiments involving blood (L set to 12, 15, or 17 mm), we used a protocol consisting of six deoxygenation cycles. A state-of-the-art multi-wavelength TD-NIRS system measured simultaneously on the two-layered medium, as well as on the deep compartment for a reference. The new method accurately determined µa (and hence StO2) in both compartments. The method is a significant progress in overcoming the contamination from the superficial layer, which is beneficial for NIRS and fNIRS applications, and may improve the determination of StO2 in the brain from measurements on the head. The advanced phantom may assist in the ongoing effort towards more realistic standardized performance tests in NIRS tissue oximetry. Data and MATLAB codes used in this study were made publicly available.

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Section: Resultssupporting

confidence: 92%

“…more recently in Refs. [ 28 , 33 – 36 ]. We will use the Levenberg–Marquardt algorithm (LMA), which allows solving nonlinear iterative least squares minimization problems [ 37 , 38 ].…”

Section: Introductionmentioning

confidence: 99%

Two-layered blood-lipid phantom and method to determine absorption and oxygenation employing changes in moments of DTOFs

Sudakou¹,

Wabnitz

Liemert

et al. 2023

Biomed. Opt. Express

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“…To simulate these shifts, we model both the absorption and scattering coefficients as continuous piecewise functions that increase linearly during the laser pulse and remain constant when the laser is turned off. Recent studies in the biomedical imaging literature indicate that ramp‐increasing functions are a valid approach to model the shift in the optical properties of laser‐irradiated tissue 29 . More specifically, we let

μ_{a} ((), t) goodbreak= ({, \begin{array}{l} 0.6 t goodbreak+ 1 & if 0 \leq t \leq 5 \\ 4 & if 5 < t \leq 15 \end{array})

and

μ_{s} ((), t) goodbreak= ({, \begin{array}{l} 80 t goodbreak+ 100 & if 0 \leq t \leq 5 \\ 500 & if 5 < t \leq 15 \end{array}),

respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Recent studies in the biomedical imaging literature indicate that ramp-increasing functions are a valid approach to model the shift in the optical properties of laser-irradiated tissue. 29 More specifically, we let…”

Section: Identifying Time-varying Absorption and Scatteringmentioning

confidence: 99%

Identification of tissue optical properties during thermal laser‐tissue interactions: An ensemble Kalman filter‐based approach

Arnold

Fichera

2022

Numer Methods Biomed Eng

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In this article, we propose a computational framework to estimate the physical properties that govern the thermal response of laser-irradiated tissue. We focus in particular on two quantities, the absorption and scattering coefficients, which describe the optical absorption of light in the tissue and whose knowledge is vital to correctly plan medical laser treatments. To perform the estimation, we utilize an implementation of the ensemble Kalman filter (EnKF), a type of Bayesian filtering algorithm for data assimilation. Unlike prior approaches, in this work, we estimate the tissue optical properties based on observations of the tissue thermal response to laser irradiation. This method has the potential for straightforward implementation in a clinical setup, as it would only require a simple thermal sensor, for example, a miniaturized infrared camera. Because the optical properties of tissue can undergo shifts during laser exposure, we employ a variant of EnKF capable of tracking time-varying parameters. Through simulated experimental studies, we demonstrate the ability of the proposed technique to identify the tissue optical properties and track their dynamic changes during laser exposure, while simultaneously tracking changes in the tissue temperature at locations beneath the surface. We further demonstrate the framework's capability in estimating additional unknown tissue properties (i.e., the volumetric heat capacity and thermal conductivity) along with the optical properties of interest.

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“…) because we are considering a Poisson process with uncorrelated noise [49]. Both cases represent different states of information that may be considered according to the situation.…”

Section: Bayes Model Selection In 2d Mediummentioning

confidence: 99%

A comparison between plausible models in layered turbid media with geometrical variations applying a Bayesian selection criterion

Vera¹,

Baez²,

García³

et al. 2020

Biomed. Phys. Eng. Express

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One possible application of Near Infrared techniques is to analyze human brain metabolic activity. Currently used models take into account the layered structure of the human head but, usually, they do not consider the non-planar surface of some of the boundaries, i.e. gray matter, which results in a much more complex structure, thus leading to more sophisticated models and longer calculation times. The main objective of this work is to determine if it is worth to replace a planar layered structure by a non-planar one. To this end we implement a Bayesian-based quantitative methodology for choosing between two competitive models describing light propagation in layered turbid media. Experiments of time-resolved diffuse reflectance measurements are performed in layered phantoms and complemented with numerical calculations. The resulting Distributions of Time of Flight of both models are compared using Bayesian model selection analysis. The non-planar interface was introduced in the simulations by a simple surface parametrization. Results suggest that, under certain conditions, a multilayer model with planar boundaries is good enough.

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Implementation of the extended Kalman filter for determining the optical and geometrical properties of turbid layered media by time-resolved single distance measurements

Cited by 4 publications

References 26 publications

Two-layered blood-lipid phantom and method to determine absorption and oxygenation employing changes in moments of DTOFs

Two-layered blood-lipid phantom and method to determine absorption and oxygenation employing changes in moments of DTOFs

Identification of tissue optical properties during thermal laser‐tissue interactions: An ensemble Kalman filter‐based approach

A comparison between plausible models in layered turbid media with geometrical variations applying a Bayesian selection criterion

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