Ran Liao

Application of sphere-cylinder scattering model to skeletal muscle.

By comparing the spatially resolved unpolarized, polarized reflectance and Mueller matrix elements of skeletal muscle with a scattering medium containing polystyrene microspheres and silk fibers, we demonstrate that the sphere-cylinder scattering model (SCSM) can reproduce the characteristic features of skeletal muscle. Both experiments and polarization sensitive Monte Carlo simulation provide evidences that SCSM may be used to characterize the structural and optical properties of skeletal muscle.

Two-dimensional backscattering Mueller matrix of sphere-cylinder scattering medium

We present the experimental results for the two-dimensional backscattering Mueller matrix of a scattering medium containing polystyrene microspheres and silk fibers and simulate the same Mueller matrix using a polarization-sensitive Monte Carlo program with both layered and homogeneous sphere-cylinder scattering models. We discuss the characteristic features in each Mueller matrix element and their relations with the parameters of the spherical and cylindrical scatterers in the medium. Both experiments and simulations suggest that the Mueller matrix elements can be used to characterize the structural and optical properties of anisotropic scattering media.

A possible quantitative Mueller matrix transformation technique for anisotropic scattering media/Eine mögliche quantitative Müller-Matrix-Transformations-Technik für anisotrope streuende Medien

Abstract By conducting both the experiments on samples containing well-aligned fibers and Monte Carlo simulations based on the sphere cylinder scattering model (SCSM), we present a Mueller matrix transformation (MMT) method for quantitatively characterizing the properties of anisotropic scattering media. We obtained a set of parameters by fitting the Mueller matrix elements to trigonometric curves in polar coordinates. These new parameters can be expressed as analytical functions of the Mueller matrix elements and display simple relationships to the structural and optical properties of the anisotropic scattering media, such as the anisotropy, the direction of the fibers, and the sizes of the scatterers. Experimental results on biological tissues show that these new parameters can be used in biomedical research. However, further studies are still necessary to correlate the MMT parameters to pathological features. Zusammenfassung Mit der Durchführung von Experimenten an Proben mit gut ausgerichteten Fasern sowie von Monte-Carlo-Simulationen basierend auf dem Kugel-Zylinder-Streumodell (sphere cylinder scattering model, SCSM) wird eine Müller-Matrix-Transformations (MMT)-Methode zur quantitativen Charakterisierung der Eigenschaften von anisotropen Streumedien vorgestellt. Durch die Anpassung („Fit“) der Müller-Matrix-Elemente an trigonometrische Kurven in Polarkoordinaten erhält man eine Vielzahl von Parametern. Diese neuen Parameter können als analytische Funktion der Müller-Matrix-Elemente ausgedrückt werden und zeigen einfache Beziehungen zu den strukturellen und optischen Eigenschaften des anisotropen Streumediums, wie z.B. der Anisotropie, der Richtung der Fasern und der Größe der Streuer. Experimentelle Ergebnisse an biologischen Geweben zeigen, dass diese neuen Parameter in der biomedizinischen Forschung verwendet werden können. Dennoch sind weitere Studien notwendig, um die MMT-Parameter mit pathologischen Merkmalen zu korrelieren.

Two-dimensional backscattering Mueller matrix of sphere-cylinder birefringence media

Abstract. We have developed a sphere–cylinder birefringence model (SCBM) for anisotropic media. The new model is based on a previously published sphere–cylinder scattering model (SCSM), but the spherical and cylindrical scatterers are embedded in a linearly birefringent medium. A Monte Carlo simulation program for SCBM was also developed by adding a new module to the SCSM program to take into account the effects of birefringence. Simulations of the backscattering Mueller matrix demonstrate that SCBM results in better agreement with experimental results than SCSM and is more suitable to characterize fibrous tissues such as skeletal muscle. Using Monte Carlo simulations, we also examined the characteristics of two-dimensional backscattering Mueller matrix of SCBM and analyzed the influence of linear birefringence.

Rotating linear polarization imaging technique for anisotropic tissues

A novel rotating linear polarization imaging technique is developed to characterize the anisotropic properties of tissues. Differences of orthogonal linear polarization with different incident and detection polarization angles are fitted to an analytical function to retrieve a set of parameters. Experiments with different tissues and Monte Carlo simulations indicate that two of the parameters, G and phi(3)2, are correlated to the anisotropic property and the orientation angle of the fibrous structure in the media. The technique can be used for clinical diagnosis.

Two-dimensional and surface backscattering Mueller matrices of anisotropic sphere-cylinder scattering media: a quantitative study of influence from fibrous scatterers

Abstract. We present both the two-dimensional backscattering point-illumination and surface-illumination Mueller matrices for the anisotropic sphere-cylinder scattering media. The experimental results of the microsphere-silk sample show that the Mueller matrix elements of an anisotropic scattering medium are different from those of an isotropic medium. Moreover, both the experiments and Monte Carlo simulations show that the directions of the fibrous scatterers have prominent effects on the Mueller matrix elements. As the fibrous samples rotate, the surface-illumination Mueller matrix measurement results for the m12, m21, m13, m31, m22, m23, m32, and m33 elements represent periodical variations. Experiments on skeletal muscle and porcine liver tissue samples confirm that the periodical changes for the surface-illumination Mueller matrix elements are closely related to the well aligned fibrous scatterers. The m22, m23, m32, and m33 elements are powerful tools for quantitative characterization of anisotropic scattering media, including biological tissues.

A study on forward scattering Mueller matrix decomposition in anisotropic medium

In this work, we apply Mueller matrix polar decomposition (MMPD) method in a forward scattering configuration on anisotropic scattering samples and look for the physics origin of depolarization and retardance. Using Monte Carlo simulations on the sphere-cylinder birefringence model (SCBM), and forward scattering experiments on samples containing polystyrene microspheres, well-aligned glass fibers and polyacrylamide, we examine in detail the relationship between the MMPD parameters and the microscopic structure of the samples. The results show that the spherical scatterers and birefringent medium contribute to depolarization and retardance respectively, but the cylindrical scatterers contribute to both. Retardance due to the cylindrical scatterers changes with their density, size and order of alignment. Total retardance is a simple sum of both contributions when cylinders are in parallel to the extraordinary axis of birefringence.

Penetration depth of linear polarization imaging for two-layer anisotropic samples

Polarization techniques can suppress multiply scattering light and have been demonstrated as an effective tool to improve image quality of superficial tissues where many cancers start to develop. Learning the penetration depth behavior of different polarization imaging techniques is important for their clinical applications in diagnosis of skin abnormalities. In the present paper, we construct a two-layer sample consisting of isotropic and anisotropic media and examine quantitatively using both experiments and Monte Carlo simulations the penetration depths of three different polarization imaging methods, i.e., linear differential polarization imaging (LDPI), degree of linear polarization imaging (DOLPI), and rotating linear polarization imaging (RLPI). The results show that the contrast curves of the three techniques are distinctively different, but their characteristic depths are all of the order of the transport mean free path length of the top layer. Penetration depths of LDPI and DOLPI depend on the incident polarization angle. The characteristic depth of DOLPI, and approximately of LDPI at small g, scales with the transport mean free path length. The characteristic depth of RLPI is almost twice as big as that of DOLPI and LDPI, and increases significantly as g increases.

Division of focal plane polarimeter-based 3 × 4 Mueller matrix microscope: a potential tool for quick diagnosis of human carcinoma tissues

Abstract. A polarization microscope is a useful tool to reveal the optical anisotropic nature of a specimen and can provide abundant microstructural information about samples. We present a division of focal plane (DoFP) polarimeter-based polarization microscope capable of simultaneously measuring both the Stokes vector and the 3×4 Mueller matrix with an optimal polarization illumination scheme. The Mueller matrix images of unstained human carcinoma tissue slices show that the m24 and m34 elements can provide important information for pathological observations. The characteristic features of the m24 and m34 elements can be enhanced by polarization staining under illumination by a circularly polarized light. Hence, combined with a graphics processing unit acceleration algorithm, the DoFP polarization microscope is capable of real-time polarization imaging for potential quick clinical diagnoses of both standard and frozen slices of human carcinoma tissues.

QUANTITATIVE MUELLER MATRIX POLARIMETRY TECHNIQUES FOR BIOLOGICAL TISSUES

We propose and conduct both the rotating linear polarization imaging (RLPI) and Mueller matrix transformation (MMT) measurements of different biological tissue samples, and testify the capability of the Mueller matrix polarimetry for the anisotropic scattering media. The independent parameters extracted from the RLPI and MMT techniques are compared and analyzed. The tissue experimental results show that the parameters are closely related to the structural characteristics of the turbid scattering media, including the sizes of the scatterers, the angular distribution and order of alignment of the fibers. The results and conclusions in this paper may provide a potential method for the detection of precancerous and early stage cancerous tissues. Also, such studies represent the Mueller matrix transformation procedure which results in a set of parameters linking up the Mueller matrix elements to the structural and optical properties of the media.