Early identification of abnormal pulmonary infectious diseases using unsupervised anomaly detection.

Background: The early identification of abnormal pulmonary infectious diseases (APIDs) could effectively control the large-scale spread of such diseases. This study proposed a deep learning-based method for the early identification of APIDs. Methods: Unsupervised anomaly detection (UAD) refers to the identification of abnormal samples of which its distribution differs from that of normal samples using a training set comprised of only normal samples. Building on this principle, we proposed a method for the early identification of APIDs. First, we established a pulmonary infection computed tomography (PICT) image sequence dataset, which included computed tomography (CT) image sequences of various common pulmonary infections, as well as two known abnormal cases [coronavirus disease 2019 (COVID-19) and melioidosis pneumonia]. Under our framework, only common infection sequences were used to train the UAD network, while both common and abnormal sequences were used in testing to assess the capability of the network to identify deviations. This approach not only detected the two known abnormal cases but was also able to detect unknown APIDs. To enhance the detection accuracy (ACC) of our approach, we developed the local reconstruction autoencoder (LRAE), which focuses on local regions in PICT images to effectively distinguish between common and abnormal infection areas. Results: Comprehensive experiments on the PICT dataset were conducted using metrics such as the area under the curve (AUC), F1-score, and ACC, and the results revealed the effectiveness and superiority of the LRAE compared to existing UAD methods. Specifically, the AUC, F1-score, and ACC of the LRAE in detecting COVID-19 CT image sequences were 0.8269, 0.7242, and 0.7801, respectively; while those for the melioidosis pneumonia CT image sequences were 0.8716, 0.6415, and 0.8146, respectively. Conclusions: This work offers a robust solution for the early identification of both known and emerging APIDs. The developed LRAE showed remarkable performance in detecting abnormal PICT image sequences.