- 學位論文
一個用於消化道中膠囊內視鏡定位的訊號處理技術
Locating Capsule Endoscope in Gastrointestinal Tract Using Signal Processing Techniques.
摘要
膠囊內視鏡系統透過吞服膠囊大小的無線攝影機進行檢查，可降低患者接受傳統內視鏡檢測的心理恐懼與身體上的不適。膠囊內視鏡系統可將腸胃道的內視鏡影像，以無線方式傳輸至患者身上攜帶的輕便接收機；待接收完畢後，再將影像傳至桌上型電腦播放，做為研判病情的重要依據。任何可疑影像及其在消化道中之對應位置對醫師都是有重要參考價值的資訊，如何自動找出這樣的資訊便是本篇論文的目的。 本論文以訊號處理技術為基礎，發展出一套有別於常見之磁浮系統膠囊內視鏡定位的方法。本論文所介紹之定位系統係利用穿戴於患者身上之天線感應陣列，配合電磁波隨距離平方衰減的原理，擷取各天線所接收之電磁波訊號的功率，進而估測出膠囊內視鏡於人體中之位置。本論文提出的定位系統將人體正面上半身分為16區且定位結果以其中一區呈現，並採用多種定位方法及輔助方法進行實驗，其中定位方法包括最大值定位法、圓半徑定位法、球半徑定位法等，同時系統採用各區不等權重、三角質心定位及多數決等輔助方法，期望能提高定位的準確性。 為了證明本論文所提技術的可行性，我們在空氣介質、生理食鹽水模擬、豬肉離體與豬隻動物實驗的多種環境下進行驗證。結果發現上述各種不同定位方法皆具有一定的正確率(區別出正確之區域)，且球半徑定位法表現最好，定位時可達到8成以上之正確率。實驗亦發現本論文所採用的定位方式可將誤差控制在5公分的2倍標準差(2DRMS)內，亦即有95%的機會，位置估測值會落在以距離膠囊內視鏡真實位置5公分為半徑的圓內。因此，本論文所提出的方法可望應用於真實應用之中。
並列摘要
In a capsule endoscope system, a capsule-like wireless camera is swallowed by a patient for medical examination. It can reduce the patient’s fearfulness and uncomfortableness resulting from the use of a traditional endoscope system. The capsule endoscope can transmit the images of gastrointestinal tract taken by the camera to a receiver carried by the patient. Then the images can be played on a personal computer and viewed by a physician for diagnosis. The physician is interested in any suspected image and its corresponding location at which it is taken. Therefore, the position of capsule endoscope at any time in the gastrointestinal tract is valuable information for the physician. How to find this piece of information automatically is the objective of this thesis. This thesis proposes a positioning approach based on signal processing techniques. The proposed approach is quite different from the traditional one which is based on magnetic levitation. The system proposed in this thesis uses an antenna array worn by the patient to receive the signal from the capsule endoscope. The position of the capsule endoscope is estimated based on the power reading sensed by each antenna and the principle that the received electromagnetic power is inversely proportional to the square of the distance between a transmitter and its intended receiver. In the proposed positioning system, the upper front human body is divided uniformly into 16 areas and the positioning result is given in terms of one of the 16 areas. Several positioning techniques along with auxiliary schemes are used in the experiment. The positioning techniques include the maximum-value method, the circle-based method, and the spherical-based method. The system also uses auxiliary schemes such as unequal weights for different areas, center of gravity, and majority voting to improve the accuracy of positioning results. In order to verify the feasibility of the proposed approach, we perform experiments in the environments of free space, normal saline in a tank, pork meat, and pig’s body, respectively. All positioning techniques give reasonable accuracy (with area correctly determined) and the spherical-based method performs the best. The accuracy can be as high as more than 80%. The experiments also show that the proposed positioning techniques can control the position error to be within 5 cm of 2-times standard deviation (2DRMS). It generally means that with 95% of chance, the position estimates will fall within the circle whose center is at the true location of the capsule endoscope and the radius is 5 cm. Thus, the proposed approach can be promising for real-world applications.