利用雷射散斑影像建立視網膜血管特性化

Abstract

我們建立了一套光學架構，透過它取得兔子眼底視網膜的散斑影像。藉由散斑對比分析，我們可以得到血流流速的資訊與相關時間常數。相關時間常數不只能用來計算流速，也可以同時視為血管彈性的間接參數。我們使用了兩種方式計算相關時間常數，一種是透過散斑對比分析的近似公式直接由對比數值運算相關時間常數，另一種是透過訊號處理中的相關方法分析。為了比較兩種方法的成效，我們取了散斑影像上的兩個區域，分別是有包含血管的與沒有包含血管的。兩種計算方法中，相關時間常數於兩種不同區域都有明顯不一樣的數值，可以用來鑑別與區分有無血管存在(流速發生)。然而，我們目前可以得到的所有數據都只是相對數值，並非絕對數值，要能得到真正的相關時間常數，建立物體運動模型與校正將是必要的。

An optical system for acquiring speckle images from rabbit retina is built. Speckle contrast analysis provides the information of blood flow and the correlation time constant, as the flow parameter, could also be seen as the elastic property index. We calculate the correlation time constant in two approaches, one is utilizing asymptotic equations from speckle contrast result, and another is correlation based approach. To determine the performance, we compare two regions with different properties, one region contains blood vessel while another doesn’t. Both approaches shows distinct differences in the value of correlation time constant from two regions. In this study, the relative correlation time constant value is acquired, yet to reach the absolute correlation time constant, a complete model need to be constructed.