Scattering and absorption of turbid materials determined from reflection measurements. 1: theory.
TL;DR: Comparison of the results indicates the range of values of the scattering and absorption parameters where the computationally fast diffusion approach is applicable.
Abstract: To allow the determination of scattering and absorption parameters of a turbid material from reflection measurements the relation of these parameters to the reflection has been described by two theoretical approaches. One approach is based on the diffusion theory which has been extended to include anisotropic scattering. This results in a reflection formula in which the scattering and absorption are described by one parameter each. As a second more general approach a Monte Carlo model is applied. Comparison of the results indicates the range of values of the scattering and absorption parameters where the computationally fast diffusion approach is applicable.
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TL;DR: A review of methods for the forward and inverse problems in optical tomography can be found in this paper, where the authors focus on the highly scattering case found in applications in medical imaging, and to the problem of absorption and scattering reconstruction.
Abstract: We present a review of methods for the forward and inverse problems in optical tomography. We limit ourselves to the highly scattering case found in applications in medical imaging, and to the problem of absorption and scattering reconstruction. We discuss the derivation of the diffusion approximation and other simplifications of the full transport problem. We develop sensitivity relations in both the continuous and discrete case with special concentration on the use of the finite element method. A classification of algorithms is presented, and some suggestions for open problems to be addressed in future research are made.
2,609Â citations
TL;DR: A simple model is developed, based on the diffusion approximation to radiative transfer theory, which yields analytic expressions for the pulse shape in terms of the interaction coefficients of a homogeneous slab.
Abstract: When a picosecond light pulse is incident on biological tissue, the temporal characteristics of the light backscattered from, or transmitted through, the sample carry information about the optical absorption and scattering coefficients of the tissue. We develop a simple model, based on the diffusion approximation to radiative transfer theory, which yields analytic expressions for the pulse shape in terms of the interaction coefficients of a homogeneous slab. The model predictions are in good agreement with the results of preliminary in vivo experiments and Monte Carlo simulations.
2,242Â citations
TL;DR: This review describes optical interactions pursued for biomedical applications (fluorescence, fluorescence lifetime, phosphorescence, and Raman from cells, cultures, and tissues) and provides a descriptive framework for light interaction based upon tissue absorption and scattering properties.
Abstract: The interaction of light within tissue has been used to recognize disease since the mid-1800s. The recent developments of small light sources, detectors, and fiber optic probes provide opportunities to quantitatively measure these interactions, which yield information for diagnosis at the biochemical, structural, or (patho)physiological level within intact tissues. However, because of the strong scattering properties of tissues, the reemitted optical signal is often influenced by changes in biochemistry (as detected by these spectroscopic approaches) and by physiological and pathophysiological changes in tissue scattering. One challenge of biomedical optics is to uncouple the signals influenced by biochemistry, which themselves provide specificity for identifying diseased states, from those influenced by tissue scattering, which are typically unspecific to a pathology. In this review, we describe optical interactions pursued for biomedical applications (fluorescence, fluorescence lifetime, phosphorescence, and Raman from cells, cultures, and tissues) and then provide a descriptive framework for light interaction based upon tissue absorption and scattering properties. Finally, we review important endogenous and exogenous biological chromophores and describe current work to employ these signals for detection and diagnosis of disease.
1,230Â citations
TL;DR: The theoretical basis for near-infrared or diffuse optical spectroscopy (NIRS or DOS) is developed, and the basic elements of diffuse optical tomography (DOT) are outlined.
Abstract: This review describes the diffusion model for light transport in tissues and the medical applications of diffuse light. Diffuse optics is particularly useful for measurement of tissue hemodynamics, wherein quantitative assessment of oxy- and deoxy-hemoglobin concentrations and blood flow are desired. The theoretical basis for near-infrared or diffuse optical spectroscopy is developed, and the basic elements of diffuse optical tomography are outlined. We also discuss diffuse correlation spectroscopy, a technique whereby temporal correlation functions of diffusing light are transported through tissue and are used to measure blood flow. Essential instrumentation is described, and representative brain and breast functional imaging and monitoring results illustrate the workings of these new tissue diagnostics.
987Â citations
01 Aug 2001
TL;DR: A simple model for subsurface light transport in translucent materials that enables efficient simulation of effects that BRDF models cannot capture and a new, rapid image-based measurement technique for determining the optical properties of translucent materials.
Abstract: This paper introduces a simple model for subsurface light transport in translucent materials. The model enables efficient simulation of effects that BRDF models cannot capture, such as color bleeding within materials and diffusion of light across shadow boundaries. The technique is efficient even for anisotropic, highly scattering media that are expensive to simulate using existing methods. The model combines an exact solution for single scattering with a dipole point source diffusion approximation for multiple scattering. We also have designed a new, rapid image-based measurement technique for determining the optical properties of translucent materials. We validate the model by comparing predicted and measured values and show how the technique can be used to recover the optical properties of a variety of materials, including milk, marble, and skin. Finally, we describe sampling techniques that allow the model to be used within a conventional ray tracer.
919Â citations
Cites methods from "Scattering and absorption of turbid..."
...Only methods that consider subsurface scattering can capture the true appearance of translucent materials, such as marble, cloth, paper, skin, milk, cheese, bread, meat, fruits, plants, fish, ocean water, snow, etc....
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References
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01 Jul 1977
TL;DR: A review of basic theories and recent advances in the studies of wave propagation and scattering in random media is presented in this article, where propagation characteristics of intensities, wave fluctuations, pulse propagation, and scattering, coherence bandwidth, and coherence time of communication channels through random media are analyzed.
Abstract: This paper presents a review of basic theories and recent advances in the studies of wave propagation and scattering in random media. Examples of the random media include the atmosphere, the ocean, and biological media whose characteristics are randomly varying in time and space. The study of electromagnetic, optical, and acoustic waves in such media has become increasingly important in recent years in the areas of communication, detection, and remote-sensing. Topics covered in this paper are divided into "waves in randomly distributed scatterers," "waves in random continua," and "remote-sensing of random media." Transport theory with various approximate solutions and multiple scattering theories are discussed and their relationships are clarified. Included in the analyses are propagation characteristics of intensities, wave fluctuations, pulse propagation and scattering, coherence bandwidth, and coherence time of communication channels through random media. Remote-sensing techniques include recent advances in the use of inversion techniques to deal with ill-posed problems.
216Â citations
TL;DR: A model of the fiber optic catheter used for the spectrophotometric measurement of oxygen content in blood is developed from the theory and compared with experimental results to further substantiate the theoretical approach.
Abstract: The scattering and absorption of light by randomly oriented, discretely scattering, red blood cells imbedded in a homogeneous plasma medium can be described by the P1 approximation to the one-speed transport equation, where the cells have the dual role of anisotropic sources for first scattering events and of scattering and absorption sites for subsequent scattering events. Equations for diffuse reflectance defined for a finite size receiver in the plane of a normally incident cylindrical photon beam are derived and compared with experimental data to fundamentally justify the basic sending-receiving characteristics of a fiber optic catheter model. A model of the fiber optic catheter used for the spectrophotometric measurement of oxygen content in blood is developed from the theory and compared with experimental results to further substantiate the theoretical approach.
214Â citations
TL;DR: In this paper, a method for calculating the surface brightness distribution on a plane-parallel reflection nebula of uniform density illuminated by a star located either in front of, behind, or arbitrarily inside the scattering medium is proposed.
Abstract: A method for calculating the surface brightness distribution on a plane-parallel reflection nebula of uniform density illuminated by a star located either in front of, behind, or arbitrarily inside the scattering medium is proposed. The Monte Carlo technique is used to find solutions to the radiative transfer problem. The scattering properties of the nebular particles are parameterized by the albedo for single scattering and a three-parameter analytic phase function. Calculations are then presented for the surface brightness distribution across the face of such nebulae with (1) a foreground star and (2) immersed stars. The calculations include the full effects of multiple scattering, are independent of a particular assumed grain material or size distribution, and are applicable to any wavelength region for which observations can be obtained.
211Â citations
TL;DR: In this article, the propagation and scattering characteristics of a short optical pulse in a dense distribution of scatterers were studied, and the integral and differential equations for the two-frequency mutual coherence function under the first-order smoothing approximation were obtained.
Abstract: This paper presents a theoretical study on propagation and scattering characteristics of a short optical pulse in a dense distribution of scatterers. Examples include pulse diffusion in whole blood and in a dense distribution of particulate matter in the atmosphere and the ocean. The parabolic equation technique is applicable to the forward-scatter region where the angular spread is confined within narrow forward angles. When the angular spread becomes comparable to the order of unit steradian, there is as much backscattering as forward scattering and diffusion phenomena take place. We start with the integral and differential equations for the two-frequency mutual coherence function under the first-order smoothing approximation, and a general diffusion equation and boundary conditions are obtained. As examples, we present solutions for diffusion of a pulse from a point source and a plane wave incident on a slab of scatterers.
150Â citations
TL;DR: This paper describes the measuring system and indicates the area of application of the method, based on reflection measurements carried out on bulk material, which will be of great advantage in many applications.
Abstract: A new experimental method has been developed to determine the scattering and absorption characteristics of a turbid material. Existing methods usually require transmission and reflection measurements carried out on a thin slab of the material under study; this method is based on reflection measurements carried out on bulk material. This will be of great advantage in many applications. This paper describes the measuring system and indicates the area of application of the method. Calibration measurements have been carried out to substantiate the approach.
141Â citations