應用於牙齒X光影像之牙齒分隔研究

Abstract

牙齒分隔在牙齒電腦輔助診斷系統，以及牙齒生物特徵辨識系統中是一個很重要的前處理動作，牙齒分隔結果的準確性，會直接影響到牙齒特徵萃取的精度，進而影響到電腦輔助診斷的結果及身份辨識的結果。因此我們提出了一個牙齒x光影像的有效牙齒分隔方法。在第一步驟中利用horizontal integral projection的資訊來分隔上下顎。在第二步驟中，我們利用了vertical integral projection配合變動視窗法及interdental papilla的資訊來分隔各個獨立的牙齒。第三步驟則是利用vertical integral projection的一階微分資訊尋找缺牙的位置，並且使用了一個型態學運算子來做影像去雜訊，再使用此去雜訊後影像做上下過度咬合或左右相鄰重疊的偵測。而實驗結果也顯示，我們的方法比已發表於文獻中的方法，更能在原始影像中出現曝光不均、大面積補牙等情形時，提供相對較好的分隔結果。

Teeth isolation is a very important pre-processing step of computer-aided dental diagnosis system and dental biometric system. The accuracy of the teeth isolation will directly affect the accuracy of feature extraction and thereby affecting the results of computer-aided diagnosis and the results of identity recognition. Therefore, we propose an effective teeth isolation method for dental X-ray images. In the first step we use the horizontal integral projection information to separate the upper and lower jaws. In the second step, we use the vertical integral projection with the dynamic window method and interdental papilla information to separate the individual teeth. The third step is to use the first derivative information of the vertical integral projection to find the location of missing teeth, and detect teeth occlusion/overlapping segments from the donoised image by bottom-hat operations. The experimental results show that our method, when compared to previous methods, gives better teeth isolation results, especially for image of uneven exposure or with large areas of dental work.