Two electric field Monte Carlo models of coherent backscattering of polarized light (original) (raw)
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Journal of The Optical Society of America A-optics Image Science and Vision, 1996
The statistical estimator concept, created in the nuclear engineering field, has been adapted to the elaboration of a new and fast semianalytical Monte Carlo numerical simulation for time-resolved light-scattering problems. This concept has also been generalized to the case of unmatched boundaries. The model, discussed in detail in this paper, contains two stages. The first stage is the information generator in which, for each scattering event, the contribution to the total reflectance and transmittance is evaluated and subtracted from the photon current energy. This procedure reduces the number of photons required to produce a given accuracy, which makes it possible to store all event positions and energies. In the second stage, called the information processor, the results of the first stage are used to calculate analytically any desired result. Examples are given for scattering slabs of isotropic or anisotropic scatterers when collimated-beam incidence is used. Reflections at the boundaries are taken into account. The results obtained either with this new method or with classical Monte Carlo methods are very similar. However, the convergence of our new model is much better and, because of the separation into two stages, any quantity related to the problem can be easily calculated afterward without recomputing the simulation.
1989
Abstruct-Using optical interaction coefficients typical of mammalian soft tissues in the red and near infrared regions of the spectrum, calculations of fluence-depth distributions, effective penetration depths and diffuse reflectance from two models of radiative transfer, diffusion theory, and Monte Carlo simulation are compared for a semi-infinite medium. The predictions from diffusion theory are shown to be increasingly inaccurate as the albedo tends to zero andlor the average cosine of scatter tends to unity.
SPIE Proceedings, 2013
Emerging clinical applications including bioluminescence imaging require fast and accurate modelling of light propagation through turbid media with complex geometries. Monte Carlo simulations are widely recognized as the standard for high-quality modelling of light propagation in turbid media, albeit with high computational requirements. We present FullMonte: a flexible, extensible software framework for Monte Carlo modelling of light transport from extended sources through general 3D turbid media including anisotropic scattering and refractive index changes. The problem geometry is expressed using a tetrahedral mesh, giving accurate surface normals and avoiding artifacts introduced by voxel approaches. The software uses multithreading, Intel SSE vector instructions, and optimized data structures. It incorporates novel hardware-friendly performance optimizations that are also useful for software implementations. Results and performance are compared against existing implementations. We present a discussion of current state-of-the-art algorithms and accelerated implementations of the modelling problem. A new parameter permitting accuracy-performance tradeoffs is also shown which has significant implications including performance gains of over 25% for real applications. The advantages and limitations of both CPU and GPU implementations are discussed, with observations important to future advances. We also point the way towards custom hardware implementations with potentially large gains in performance and energy efficiency.
Monte Carlo methods for light propagation in biological tissues
Mathematical biosciences, 2015
Light propagation in turbid media is driven by the equation of radiative transfer. We give a formal probabilistic representation of its solution in the framework of biological tissues and we implement algorithms based on Monte Carlo methods in order to estimate the quantity of light that is received by a homogeneous tissue when emitted by an optic fiber. A variance reduction method is studied and implemented, as well as a Markov chain Monte Carlo method based on the Metropolis-Hastings algorithm. The resulting estimating methods are then compared to the so-called Wang-Prahl (or Wang) method. Finally, the formal representation allows to derive a non-linear optimization algorithm close to Levenberg-Marquardt that is used for the estimation of the scattering and absorption coefficients of the tissue from measurements.
Journal of Biomedical Optics, 2014
We present a coupled forward-adjoint Monte Carlo (cFAMC) method to determine the spatially resolved sensitivity distributions produced by optical interrogation of three-dimensional (3-D) tissue volumes. We develop a general computational framework that computes the spatial and angular distributions of the forward-adjoint light fields to provide accurate computations in mesoscopic tissue volumes. We provide full computational details of the cFAMC method and provide results for low-and high-scattering tissues probed using a single pair of optical fibers. We examine the effects of source-detector separation and orientation on the sensitivity distributions and consider how the degree of angular discretization used in the 3-D tissue model impacts the accuracy of the resulting absorption sensitivity profiles. We discuss the value of such computations for optical imaging and the design of optical measurements.