Honghui He

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.

Characterizing the microstructures of biological tissues using Mueller matrix and transformed polarization parameters

Mueller matrices can be used as a powerful tool to probe qualitatively the microstructures of biological tissues. Certain transformation processes can provide new sets of parameters which are functions of the Mueller matrix elements but represent more explicitly the characteristic features of the sample. In this paper, we take the backscattering Mueller matrices of a group of tissues with distinctive structural properties. Using both experiments and Monte Carlo simulations, we demonstrate qualitatively the characteristic features of Mueller matrices corresponding to different structural and optical properties. We also calculate two sets of transformed polarization parameters using the Mueller matrix transformation (MMT) and Mueller matrix polar decomposition (MMPD) techniques. We demonstrate that the new parameters can separate the effects due to sample orientation and present quantitatively certain characteristic features of these tissues. Finally, we apply the transformed polarization parameters to the unstained human cervix cancerous tissues. Preliminary results show that the transformed polarization parameters can provide characteristic information to distinguish the cancerous and healthy tissues.

Mueller matrix polarimetry for differentiating characteristic features of cancerous tissues

Abstract. Polarization measurements allow one to enhance the imaging contrast of superficial tissues and obtain new polarization sensitive parameters for better descriptions of the micro- and macro- structural and optical properties of complex tissues. Since the majority of cancers originate in the epithelial layer, probing the morphological and pathological changes in the superficial tissues using an expended parameter set with improved contrast will assist in early clinical detection of cancers. We carry out Mueller matrix imaging on different cancerous tissues to look for cancer specific features. Using proper scattering models and Monte Carlo simulations, we examine the relationship between the microstructures of the samples, which are represented by the parameters of the scattering model and the characteristic features of the Mueller matrix. This study gives new clues on the contrast mechanisms of polarization sensitive measurements for different cancers and may provide new diagnostic techniques for clinical applications.

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.

Characterizing microstructures of cancerous tissues using multispectral transformed Mueller matrix polarization parameters

In this paper, we take the transmission 3 × 3 linear polarization Mueller matrix images of the unstained thin slices of human cervical and thyroid cancer tissues, and analyze their multispectral behavior using the Mueller matrix transformation (MMT) parameters. The experimental results show that for both cervical and thyroid cancerous tissues, the characteristic features of multispectral transmitted MMT parameters can be used to distinguish the normal and abnormal areas. Moreover, Monte Carlo simulations based on the sphere-cylinder birefringence model (SCBM) provide additional information of the relations between the characteristic spectral features of the MMT parameters and the microstructures of the tissues. Comparisons between the experimental and simulated data confirm that the contrast mechanism of the transmission MMT imaging for cancer detection is the breaking down of birefringent normal tissues for cervical cancer, or the formation of birefringent surrounding structures accompanying the inflammatory reaction for thyroid cancer. It is also testified that, the characteristic spectral features of polarization imaging techniques can provide more detailed microstructural information of tissues for diagnosis applications.

Mapping local orientation of aligned fibrous scatterers for cancerous tissues using backscattering Mueller matrix imaging

Abstract. Polarization measurements are sensitive to the microstructure of tissues and can be used to detect pathological changes. Many tissues contain anisotropic fibrous structures. We obtain the local orientation of aligned fibrous scatterers using different groups of the backscattering Mueller matrix elements. Experiments on concentrically well-aligned silk fibers and unstained human papillary thyroid carcinoma tissues show that the m22, m33, m23, and m32 elements have better contrast but higher degeneracy for the extraction of orientation angles. The m12 and m13 elements show lower contrast, but allow us to determine the orientation angle for the fibrous scatterers along all directions. Moreover, Monte Carlo simulations based on the sphere-cylinder scattering model indicate that the oblique incidence of the illumination beam introduces some errors in the orientation angles obtained by both methods. Mapping the local orientation of anisotropic tissues may not only provide information on pathological changes, but can also give new leads to reduce the orientation dependence of polarization measurements.

Probing microstructural information of anisotropic scattering media using rotation-independent polarization parameters

Polarization parameters contain rich information on the micro- and macro-structure of scattering media. However, many of these parameters are sensitive to the spatial orientation of anisotropic media, and may not effectively reveal the microstructural information. In this paper, we take polarization images of different textile samples at different azimuth angles. The results demonstrate that the rotation insensitive polarization parameters from rotating linear polarization imaging and Mueller matrix transformation methods can be used to distinguish the characteristic features of different textile samples. Further examinations using both experiments and Monte Carlo simulations reveal that the residue rotation dependence in these polarization parameters is due to the oblique incidence illumination. This study shows that such rotation independent parameters are potentially capable of quantitatively classifying anisotropic samples, such as textiles or biological tissues.

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.