Automated Endoscopic Image Classification via Deep Neural Network With Class Imbalance Loss

Recently, many computer-aided diagnosis (CAD) methods have been proposed to help physicians automatically classify endoscopic images. However, most existing methods often result in poor performance, especially for the minority classes, when the dataset is imbalanced. In this paper, we propose a new CAD method for automated endoscopic image classification by introducing a novel class imbalance (CI) loss to the classical deep neural network (DNN). Specifically, we use the DNN to extract rich feature representations. Given that the majority class usually dominates the prediction error and influences the gradient of the network, the proposed CI loss considers both the class frequency and prediction probability of the ground-truth class to assign the weight of each sample and helps the minority classes contribute more to descending the gradient in the training process than the majority classes. Thanks to the CI loss, the network pays more attention to minority classes and hard samples. To verify the effectiveness of our proposed method, we conduct comprehensive experiments in the binary-class classification task on our collected polyp recognition dataset (22,935 images) and in the multi-class classification task on the public Hyper-Kvasir dataset (10,662 images). Experimental results show that our method is competent for the imbalanced endoscopic image classification task with good performance.