Hybrid Method for Solving the Radiative Transport Equation

The spherical harmonics method (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>N</mi></msub></semantics></math></inline-formula> method) is of...

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Main Authors: André Liemert, Dominik Reitzle, Alwin Kienle
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Photonics
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Online Access:https://www.mdpi.com/2304-6732/12/5/409
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author André Liemert
Dominik Reitzle
Alwin Kienle
author_facet André Liemert
Dominik Reitzle
Alwin Kienle
author_sort André Liemert
collection DOAJ
description The spherical harmonics method (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>N</mi></msub></semantics></math></inline-formula> method) is often used for solving the radiative transport equation in terms of analytical functions. A severe and unsolved problem in this context was the evaluation of the angle-resolved radiance near sources and boundaries, which is a serious limitation of this method in view of concrete applications, e.g., in biomedical optics for investigating the different types of optical microscopy, within NIR spectroscopy, such as for the determination of ingredients in foods or in pharmaceuticals, and within physics-based rendering. In this article, we report on a hybrid method that enables accurate evaluation of the angle-resolved radiance directly at the boundary of an anisotropically scattering medium, avoiding the problems of the traditional <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>N</mi></msub></semantics></math></inline-formula> methods. The derived integral equation needed for the realization of the hybrid <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>N</mi></msub></semantics></math></inline-formula> method is formally valid for an arbitrary convex bounded medium. The proposed approach can be evaluated with practically the same computational effort as the traditional <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>N</mi></msub></semantics></math></inline-formula> method while being far more accurate.
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spelling doaj-art-44b21d59d4df4ce39a484792dd10e6b82025-08-20T03:47:57ZengMDPI AGPhotonics2304-67322025-04-0112540910.3390/photonics12050409Hybrid Method for Solving the Radiative Transport EquationAndré Liemert0Dominik Reitzle1Alwin Kienle2Institut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Helmholtzstr. 12, D-89081 Ulm, GermanyInstitut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Helmholtzstr. 12, D-89081 Ulm, GermanyInstitut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Helmholtzstr. 12, D-89081 Ulm, GermanyThe spherical harmonics method (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>N</mi></msub></semantics></math></inline-formula> method) is often used for solving the radiative transport equation in terms of analytical functions. A severe and unsolved problem in this context was the evaluation of the angle-resolved radiance near sources and boundaries, which is a serious limitation of this method in view of concrete applications, e.g., in biomedical optics for investigating the different types of optical microscopy, within NIR spectroscopy, such as for the determination of ingredients in foods or in pharmaceuticals, and within physics-based rendering. In this article, we report on a hybrid method that enables accurate evaluation of the angle-resolved radiance directly at the boundary of an anisotropically scattering medium, avoiding the problems of the traditional <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>N</mi></msub></semantics></math></inline-formula> methods. The derived integral equation needed for the realization of the hybrid <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>N</mi></msub></semantics></math></inline-formula> method is formally valid for an arbitrary convex bounded medium. The proposed approach can be evaluated with practically the same computational effort as the traditional <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>N</mi></msub></semantics></math></inline-formula> method while being far more accurate.https://www.mdpi.com/2304-6732/12/5/409radiative transportspherical harmonics methodphoton migrationturbid medialight propagation in tissues
spellingShingle André Liemert
Dominik Reitzle
Alwin Kienle
Hybrid Method for Solving the Radiative Transport Equation
Photonics
radiative transport
spherical harmonics method
photon migration
turbid media
light propagation in tissues
title Hybrid Method for Solving the Radiative Transport Equation
title_full Hybrid Method for Solving the Radiative Transport Equation
title_fullStr Hybrid Method for Solving the Radiative Transport Equation
title_full_unstemmed Hybrid Method for Solving the Radiative Transport Equation
title_short Hybrid Method for Solving the Radiative Transport Equation
title_sort hybrid method for solving the radiative transport equation
topic radiative transport
spherical harmonics method
photon migration
turbid media
light propagation in tissues
url https://www.mdpi.com/2304-6732/12/5/409
work_keys_str_mv AT andreliemert hybridmethodforsolvingtheradiativetransportequation
AT dominikreitzle hybridmethodforsolvingtheradiativetransportequation
AT alwinkienle hybridmethodforsolvingtheradiativetransportequation