Covid-19 detection from radiographs by feature-reinforced ensemble learning

The coronavirus (Covid-19) epidemic continues to have a negative influence on the global population's well-being and health. Scientists in many fields around the world are working non-stop to find a solution to the prevention of this epidemic. In the field of computer science, this struggle is supported by studies on especially the analysis of X-ray and CT images with artificial intelligence. In this study, two different ensemble learning models, including deep learning and a combination of machine learning methods, are presented for the detection of SARS-CoV-2 infection from X-ray images. The main purpose of this study is to increase the classification ability of Residual Convolutional Neural Network (ResCNN), which is used as a deep learning method, with the assist of machine learning algorithms and extracted features from images. The proposed models were validated on a total of 5228 chest X-ray images categorized as Normal, Pneumonia, and Covid-19. The images in the dataset were sized in four different ways, 32 x 32, 64 x 64, 128 x 128, and 256 x 256, in order to analyze the validity of the proposed models in more detail. These four datasets were partitioned with the 10-fold cross-validation technique and converted into a total of 40 training and test data. Both proposed models use features derived from the ResCNN as the basis and test a certain number of machine learning algorithms with a majority voting technique by dividing them into subsets. In the architecture of the second model, it combines the features extracted from the Local Binary Patterns (LBP) and Histogram of Oriented Gradients (HOG) methods in addition to the features obtained from the ResCNN. It has been seen that the classification ability of both proposed models is better than the ResCNN in the experiments. In particular, the second model gives a similar classification score even though it is tested with images four-times smaller (e.g., 32 x 32 vs. 128 x 128) than those used in the ResCNN. This shows that the model can give ideal results with lower computational cost.