上皮細胞和組織的三維折射率與光學散射特性

Abstract

癌症已然成為全球主要死亡原因之一，多數癌症的發生源自於上皮細胞層病變。癌症發生的同時將會伴隨細胞結構的改變，進而影響光學散射特性。即使，已經有許多研究團隊提出不同的光學散射診斷技術；然而，由於缺乏真實細胞與組織的三維折射率結構，因此細胞和組織的真實結構和散射的關聯性難以完整地探討與分析。因此，此研究目的主要發展定量三維折射率顯微鏡，應用此顯微鏡量測細胞和組織的折射率結構後，再使用時域有限差分法和散射相位理論模擬與計算細胞和組織光學散射特性。由食道切片實驗結果發現：組織的散射係數可以作為區分正常與癌前病變上皮組織的指標，癌前病變上皮組織散射係數高於正常組織45.2%。散射係數的上升源自於病變過程時，細胞核密度與核質比的上升；更重要的是，組織、細胞的折射率結構變化也是影響散射係數的重要參數之一。而在細胞逆散射的模擬結果呈現：組織內細胞的細胞逆散射光譜震盪主要來自於細胞核的貢獻。因此，細胞核的軸向和橫向尺寸可以分別藉由米氏散射定理擬合逆散射光譜與逆散射角度分布得知。藉由量測細胞核的尺寸，可以用來區分的正常與癌前病變的複層鱗狀上皮組織。總結，這篇論文提出研究方法除了可用以分析複層鱗狀上皮組織結構與散射關聯性外，也可應用於其它的細胞與組織研究。正常與癌前病變食道上皮細胞層散射係數的研究結果顯示漫反射技術可用於偵測上皮組織的癌前病變。此外，伴隨細胞核變大的癌前上皮組織，如子宮頸，也可利用角度或光譜逆散射強度分布配合米氏定理估計細胞核尺寸以達到早期診斷。

Cancer is one of the main causes of death in the world. Most cancers are of epithelial origin. The progression of epithelial dysplasia, a precursor of many tumors of stratified squamous epithelia, is accompanied by changes of tissue and cellular structures in the epithelium. These changes in structure are expected to alter light scattering properties of the cells and tissue. Although many light scattering diagnostic techniques have been proposed for diagnosing cancers, the complete and quantitative understanding of the correlation between scattering properties and structures of epithelial cells/tissue was difficult due to lack of realistic quantitative refractive indices distributions of cells/tissue. The current study aimed to propose a method for investigating the correlation between structures and light scattering properties of epithelial cells and tissue. Firstly, the three-dimensional refractive index microscope was developed and used for measuring the structures of cells and tissue. The scattering properties of cells and tissue were obtained by the finite-difference time-domain tool and the scattering-phase theorem. The results of investigating esophageal epithelia demonstrate that the average scattering coefficient of the precancerous epithelia was 45.2% higher than that of normal epithelia. The parameters that mainly determine the scattering coefficients are the cell density and the nuclear-to-cytoplasmic ratio which are the common indicators of histological diagnosis. The standard deviation of refractive indices of epithelial cells and tissue is also important parameter. The study of backscattering of single cell presents that for in vivo cells periodic oscillations in spectral and angular backscattering patterns are mainly dependent on the axial and transversal sizes of nuclei. The nuclear size can be extracted by fitting backscattering patterns with Mie theory. The precancerous and normal cells, for example, cervical cells, can be distinguished by estimating the nuclear sizes. In summary, the proposed analysis method can be extended for investigating the correlation between structures and scattering properties of any cells and tissue in addition to stratified squamous epithelial tissue. The study of the scattering coefficients of epithelial tissue suggests that the epithelial precancers can be early detected by using diffuse reflectance techniques measuring scattering coefficients of in vivo tissue. Additionally, the precancers of epithelial tissue, accompanied by enlarged nuclei, can be also diagnosed by sizing nuclear size by either angular or spectral backscattering patterns with Mie theory.