生物組織內光子動態擴散的量測與模擬

Measurement and Simulation of the Dynamic of Phanton Diffusion in Biological Tissue

韓之強(Chi-Chiang Han)

指導教授 ： 蔡正倫

中原大學/工學院/醫學工程研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100226

摘要

光動力治療、雷射都卜勒及血氧濃度檢測等生醫光學的應用，都需掌握生物組織的光學特性與光學參數(包括吸收係數、散射係數、非均向散射係數)，才能準確預估光線進入組織後的能量分佈範圍與光線經過的部位深度。本研究使用低同調光干涉的原理來量測光在生物組織內散射及動態擴散情形，藉以瞭解光在組織內分佈的範圍與光的擴散路徑。

此量測的基本架構為馬克詹德(Mach-Zender)干涉儀，光源使用波長650nm的雷射二極體工作在閥值以下，干涉影像以12位元的數位攝影機拍攝再以電腦作影像的分析處理。研究中也使用蒙地卡羅方法來模擬光在組織內的動態擴散情形，並製作組織假體來當作測試樣本，用來與蒙地卡羅模擬的結果做比較以為數學模型修正的依據。

研究的結果顯示低同調干涉影像可以顯示光在組織內擴散行進的情形，所拍攝到的影像除了有尚保持著同調性的斑點影像外，還有已無同調性的擴散光影像。比較假體實驗與模擬結果發現光源射入點至組織樣本表面的距離及組織樣本的散射係數，皆對所測得光在組織內擴散行進的方向與範圍有相當大的影響。在肌肉組織的量測上，發現近場的光分佈會受到紋理組織角度的影響。脂肪加熱的實驗也證明溫度是影響光分佈的因素。

關鍵字

蒙地卡羅模擬 ； 光動態擴散 ； 光學係數 ； 低同調光干涉

並列摘要

Most applications of biomedical optics, such as photodynamic therapy, laser Doppler flowmetry, and pulse oximetry require some knowledge of optical characteristics and coefficients of biological tissues in order to predict the light energy distribution and penetration depth in tissues. The most typical optical coefficients are optical absorption, scattering, and anisotropy coefficients. In this study, a low coherent interferometer system was used to detect the dynamic migration of photon in biological tissues. This measurement would be helpful in understanding how photons propagate in biological tissues.

The basic structure of the measurement system is a Mach-Zender interferometer. A diode laser with wavelength of 650nm working below threshold was used as the light source. The interference image was captured by a CCD camera with 12-bits of resolution. The images were further processed and analyzed in a personal computer. Monte Carlo model was also used in this study to simulate the dynamic migration of photon. Comparison of the results of measurement on tissue phantom can be used to verify the simulation results and to help modifying the model.

The results show that the system can acquire the dynamic migration of photons. Before processing, the light distribution image included the coherent speckle image and the noncoherent diffusive image. By comparing the results of phantom experiment and simulation, the distance from the injecting site to the measuring surface and the scattering coefficient of sample have great influence on the speckle image. The measurement on muscle tissue showed the light distribution at near field would be influence by the direction of muscle fibers. The results on heated fat tissue showed that temperature is a major factor that affected light propagation in fat tissue.

並列關鍵字

Optical coefficient ； Dynamic migration of photon

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