Development of CNN-LSTM combinational architecture for COVID-19 detection

The world has been under extreme pressure due to the spread of the coronavirus. The urgency to eradicate the virus has caused distress amongst civilians and medical agencies to an equal extent. Due to anomalies observed in the results from reverse transcription-polymerase chain reaction (RTPCR) tests, more reliable options like computed tomography (CT) scan-based tests are being researched upon. In this paper, a novel combinational architecture is built upon the principles of Convolution Neural Networks (CNN) and Long Short Term Memory (LSTM) Networks to detect COVID-19 virus. This method uses chest X-ray images as inputs to combinational architecture for the classification of samples. The CNN part of the network will be used to extract features that help in the classification, and the LSTM part will be used for classification based on the extracted features. A total of 8 convolutional layers and 4 pooling layers are used for CNN and 4 LSTM layers of 64 and 128 cells respectively. Instead of the sigmoid function, a rectified linear unit function is used as an activation function. This provides non-linearity to the CNN and better accuracies in comparison. The proposed model employs a padding layer to prevent the loss of information. Accuracy, loss, F1 score, and Matthew's Correlation Coefficient (MCC) are calculated to analyse the effectiveness of the proposed architecture. The proposed model is validated using a relatively larger dataset of 7292 images. The combinational architecture provides a more informative and truthful result in the evaluation of classification as it caters to both the size of positive elements and negative elements in the dataset. The proposed CNN-LSTM model gives an accuracy of 98.91% and an MCC value of 97.84% respectively. The model is also compared with models employing transfer learning methods for similar applications.