We have studied the optical properties of mammalian cell suspensions to provide a mechanistic basis for interpreting tissues in vivo. Measurements wavelength dependence reduced scattering coefficient and measurements phase function demonstrated that there is distribution scatterer sizes. The volumes scatterers are equivalent those spheres with diameters range between ~0.4 2.0 mum. isolated organelles indicate mitochondria other similarly sized responsible at large angles, whereas nuclei...

We analyse the limits of diffusion approximation to time-independent equation radiative transfer for homogeneous and heterogeneous biological media. Analytical calculations finite-difference simulations based on theory are compared with discrete-ordinate, transport calculations. The influence ratio absorption scattering coefficient accuracy quantified different definitions coefficient, D, discussed. also address effects caused by void-like heterogeneities in which very small surrounding...

We report on the first three-dimensional, volumetric, tomographic localization of vascular reactivity in brain. To this end we developed a model-based iterative image reconstruction scheme that employs adjoint differentiation methods to minimize difference between measured and predicted data. The necessary human-head geometry optode locations were determined with photogrammetric method. illustrate performance technique, three-dimensional distribution changes concentration oxyhemoglobin,...

Currently available tomographic image reconstruction schemes for optical tomography (OT) are mostly based on the limiting assumptions of small perturbations and a priori knowledge properties reference medium. Furthermore, these algorithms usually require inversion large, full, ill-conditioned Jacobian matrixes. In this work gradient-based iterative (GIIR) method is presented that promises to overcome current limitations. The code consists three major parts: (1) A finite-difference,...

We present experimental results that show the spatial variations of diffuse-backscattered intensity when linearly polarized light is incident upon highly scattering media. Experiments on polystyrene-sphere and Intralipid suspensions demonstrate radial azimuthal observed pattern depend concentration, size, anisotropy factor g particles constitute medium. Measurements performed biological-cell potential this method for cell characterization.

We have developed a Monte Carlo algorithm that computes all two-dimensional elements of the diffuse backscattering Mueller matrix for highly scattering media. Using Stokes–Mueller formalism and amplitudes calculated with Mie theory, we are able to consider polarization-dependent photon propagation in media, including linearly circularly polarized light. The numerically determined compared experimental data different particle sizes show good agreement both azimuthal radial direction.

We report the development of a heterogeneous resin-tube model to study influence blood vessels on apparent absorption system, mu a(sys), using time-resolved technique. The experimental results show that a(sys) depends inside tubes, a(tube), tube diameters, and tube-to-sample volume ratios. A mathematical expression relating a(tube) is derived based verified by Monte Carlo simulations for models. This analytical formula predicts coefficient measured biological organ volume-weighted sum...

We report on the development of a method that records spatially dependent intensity patterns polarized light is diffusely backscattered from highly scattering media. It demonstrated these can be used to differentiate turbid media, such as polystyrene-sphere and biological-cell suspensions. Our technique employs He-Ne laser (l=543nm), which focused onto surface medium. A area approximately 4x4 cm centered input point imaged through polarization-analysis optics CCD camera. One observe large...

In this article, we describe the design rationale and performance features of an integrated multichannel continuous wave (cw) near-infrared (NIR) optical tomographic imager capable collecting fast measurements over a large dynamic range. Fast data collection (∼70 Hz/channel/wavelength) is achieved using time multiplexed source illumination (up to 25 sites) combined with frequency encoded wavelength discrimination four-wavelength capability) parallel detection (32 detectors). The described...

Many methods of optical tissue diagnosis require that measurements be performed with small source-detector separations in a backscatter geometry. Monte Carlo simulations are used to demonstrate for these situations light transport depends on the exact form angular scattering probability distribution, P(theta). Simulations different forms P(theta) same value ?cos theta? result collection significantly fractions incident photons, particularly when small-numerical-aperture delivery and fibers...

Optical tomography consists of reconstructing the spatial distribution absorption and scattering properties a medium from surface measurements transmitted light intensities. Mathematically, this problem amounts to parameter identification for equation radiative transfer (ERT) with diffusion‐type boundary measurements. Because they are posed in phase‐space, equations quite challenging solve computationally. Most past works have considered steady‐state ERT or diffusion approximation ERT. In...

We present a novel optical tomographic imaging system that was designed to determine two-dimensional spatial distribution of properties in sagittal plane through finger joints. The incorporates single laser diode and silicon photodetector into scanning device records spatially resolved light intensities as they are transmitted finger. These data input model-based iterative image reconstruction (MOBIIR) scheme, which uses the equation radiative transfer (ERT) forward model for propagation...

Diffuse optical tomography has shown promising results as a tool for breast cancer screening and monitoring response to chemotherapy. Dynamic imaging of the transient an external stimulus, such pressure or respiratory maneuver, can provide additional information that be used detect tumors. We present new digital continuous-wave system designed simultaneously image both breasts at fast frame rates with large number sources detectors. The uses master-slave signal processor-based detection...

There has been recent and growing interest in applying Cerenkov radiation (CR) for biological applications. Knowledge of the production efficiency other characteristics CR produced by various radionuclides would help accessing feasibility proposed applications guide choice radionuclides. To generate this information we developed models based on Frank-Tamm equation distribution Monte-Carlo simulations photon β particle transport. All were validated against direct measurements using multiple...

The applicability of diffusion theory for the determination tissue optical properties from time-resolved reflectance spectroscopy is investigated. Analytical expressions using three most commonly assumed boundary conditions at air-tissue interface are compared with Monte Carlo simulations and measurements on phantoms. effects choice accuracy findings parameters quantified, criteria accurate curve-fitting algorithms developed.

The objective of this study was to determine whether there are intrinsic differences in the light scattering properties tumorigenic and nontumorigenic cells from a multistep carcinogenesis model.Wavelength-dependent polarization-dependent cell suspensions were measured.Statistically significant found between cells. CONCLUSIONS. Differences attributed change average size centers on order few ten nanometers. This work is relevant development noninvasive optical methods for cancer diagnosis.

The quantification of a nonuniform quantum yield or fluorophore absorption distribution is major interest in molecular imaging biological tissue. We introduce what believed to be the first fluorescence image reconstruction algorithm based on equation radiative transfer that recovers spatial light-emitting fluorophores inside highly scattering medium from measurements made surface medium. obtain images either absorption.

We present an algorithm that provides a frequency-domain solution of the equation radiative transfer (ERT) for heterogeneous media arbitrary shape. Although ERT is more accurate than diffusion equation, no code widely employed case has been developed to date. In this work discretized by combination discrete-ordinate and finite-volume methods. Two numerical simulations are presented.

We introduce a transport-theory-based PDE-constrained multispectral model for direct imaging of the spatial distributions chromophores concentrations in biological tissue. The method solves forward problem (boundary radiance at each wavelength) and inverse (spatial distribution concentrations), an all-at-once manner framework reduced Hessian sequential quadratic programming method. To illustrate code's performance, we present numerical experimental studies involving tumor bearing mice. It is...

Diffuse optical tomography (DOT) is a noninvasive, nonionizing imaging modality that uses near-infrared light to visualize optically relevant chromophores. A recently developed dynamic DOT system enables the study of hemodynamic effects in breast during breath-hold. Dynamic was performed total 21 subjects (age 54±10 years ) including 3 healthy and 18 with benign (n=8 malignant (n=14 masses. Three-dimensional time-series images percentage change oxygenated deoxygenated hemoglobin...