利用有限差分時域法來模擬正常細胞和病變細胞的細胞散射光

Abstract

癌症是一個人類仍然感到棘手的疾病，而其中對於癌症和正常細胞在光學上的散射特性，尤其是細胞的散射光譜，如果能開發一套模擬工具去模擬，把細胞散射和折射率或細胞大小的關係量化，找出正常細胞與病變細胞的不同，有機會可以實踐光學非侵入式的癌前病變檢測。 本篇論文主要使用的模擬方法為有限差分時域（FDTD）法，利用馬克斯威爾方程式做基礎來做散射物的模擬，此方法可以很彈性的調變散射物的介電系數和形狀，甚至式入射波的形狀等等，來做不同的模擬，我們可以利用此方法做正常細胞和癌症細胞的模擬，並藉由癌症細胞和正常細胞結構和折射率的不同，找出折射率或大小等參數和細胞散射場可能的關係。 而本篇所使用的細胞模型，是用近年發展的相位顯微術(Tomography Phase Microscopy)，以實驗的方式取得以前論文無法取得之細胞三維的折射率分布影響以及細胞的型態，大大提升模擬的精確度以及可信度。

Tumor now is still a troublesome disease for human. Since light scattering is very sensitive to the cell structure and refractive index, if I could build up the tool to simulate the light scattering phenomenon of different kind of cells such as cancer and normal,and it may be a potential database for clinical diagnosis for non-invasive epithelium cancer in the future.

In my thesis, I apply finite difference time domain (FDTD) method to build up my simulation tool. The FDTD method is based on Maxwell Equations in Electromagnetics. Furthermore, It is very flexible and reliable methods that you can modify many parameters such as structure or refractive index of scattering objects, and even the waveform incident wave. We can use this method to simulate the light scattering of cancerous cell and normal cell and try to find there feature by FDTD method. Last but not least, I also make use of the data obtained from the Tomography Phase Microscopy, which could provide the precise three dimensional refractive index composition of cell and even the morphology of cell. This is the kind of breakthrough that we can simulate the light scattering of cell using the exact experimental data but not an refractive index average of the cell which are usually used by previous research.