LPICM, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Palaiseau, France.
Tsinghua University, Department of Physics, Beijing, China.
J Biomed Opt. 2020 Jan;25(1):1-11. doi: 10.1117/1.JBO.25.1.015002.
: Definitive diagnostics of many diseases is based on the histological analysis of thin tissue cuts with optical white light microscopy. Extra information on tissue structural properties obtained with polarized light would help the pathologist to improve the accuracy of his diagnosis.
We report on using Mueller matrix microscopy data, logarithmic decomposition, and polarized Monte Carlo (MC) modeling for qualitative and quantitative analysis of thin tissue cuts to extract the information on tissue microstructure that is not available with a conventional white light microscopy.
Unstained cuts of human skin equivalents were measured with a custom-built liquid-crystal-based Mueller microscope in transmission configuration. To interpret experimental data, we performed the simulations with a polarized MC algorithm for scattering anisotropic media. Several optical models of tissue (spherical scatterers within birefringent host medium, and combination of spherical and cylindrical scatterers within either isotropic or birefringent host medium) were tested.
A set of rotation invariants for the logarithmic decomposition of a Mueller matrix was derived to rule out the impact of sample orientation. These invariants were calculated for both simulated and measured Mueller matrices of the dermal layer of skin equivalents. We demonstrated that only the simulations with a model combining both spherical and cylindrical scatterers within birefringent host medium reproduced the experimental trends in optical properties of the dermal layer (linear retardance, linear dichroism, and anisotropic linear depolarization) with layer thickness.
Our studies prove that Mueller polarimetry provides relevant information not only on a size of dominant scatterers (e.g., cell nuclei versus subwavelength organelles) but also on its shape (e.g., cells versus collagen fibers). The latter is directly related to the state of extracellular collagen matrix, which is often affected by early pathology. Hence, using polarimetric data can help to increase the accuracy of diagnosis.
许多疾病的明确诊断都基于对薄组织切片的组织学分析，通过光学白光显微镜进行。利用偏光获得的关于组织结构特性的额外信息将有助于病理学家提高诊断的准确性。
我们报告了使用穆勒矩阵显微镜数据、对数分解和偏振蒙特卡罗（MC）建模来对薄组织切片进行定性和定量分析，以提取常规白光显微镜无法获得的组织微观结构信息。
使用基于液晶的定制穆勒显微镜在传输配置下对未经染色的人体皮肤等效物切片进行了测量。为了解释实验数据，我们使用偏振 MC 算法对各向异性散射介质进行了模拟。我们测试了几种组织光学模型（双折射介质中的球形散射体，以及各向同性或双折射介质中球形和圆柱形散射体的组合）。
为了排除样品取向的影响，推导出了对数分解穆勒矩阵的一组旋转不变量。对皮肤等效物真皮层的模拟和测量穆勒矩阵都计算了这些不变量。我们证明，只有在一个模型中，同时包含双折射介质中的球形和圆柱形散射体的模型才能模拟出真皮层光学特性（线性延迟、线性二色性和各向异性线性退偏）与层厚度的实验趋势。
我们的研究证明，穆勒偏振计不仅提供了关于主导散射体（例如，细胞核与亚波长细胞器）大小的相关信息，还提供了关于其形状（例如，细胞与胶原纤维）的相关信息。后者与细胞外胶原基质的状态直接相关，而细胞外胶原基质的状态通常受早期病理的影响。因此，使用偏振数据可以帮助提高诊断的准确性。
