Wireless capsule endoscopy (WCE) plays an important role in diagnosing gastrointestinal tract diseases. Efficiently pinpointing the pylorus and ileocecal valve, which mark the start and end of the small intestine, is vital for clinicians determining the location of abnormalities in gastrointestinal tract as soon as possible during burdensome reviewing work. In this study, a novel and fault-tolerant automatic locating system for pylorus and ileocecal valve was proposed, combining a ResNet-50-based gastrointestinal classification model and the sliding pin algorithm. The classification model classified the WCE images into three categories, separated by the small intestine. And then the sliding pin algorithm was created to pinpoint the location of the pylorus and ileocecal valve even if there were misclassifications. A total of 108,542 WCE images were used to train and test the gastrointestinal classification model. The average accuracy of classification model was 92.21% with recognition rate varying from 88% to 96%. Furthermore, thirty-one independent WCE cases were selected to verify the proposed locating method. The mean locating error was 26 frames for the pylorus and 65 frames for the ileocecal valve, which was notably smaller than those of other state-of-the-art methods. In conclusion, this study presented an innovative approach for automatically locating the boundary of small intestine in WCE. The promising results indicated that this method was able to accurately identify the pylorus and ileocecal valve, which was expected to improve the endoscopic diagnostic efficiency of gastrointestinal diseases.
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