Development of a chest X-ray machine learning convolutional neural network model on a budget and using artificial intelligence explainability techniques to analyze patterns of machine learning inference

Objective: Machine learning (ML) will have a large impact on medicine and accessibility is important. This study's model was used to explore various concepts including how varying features of a model impacted behavior. Materials and Methods: This study built an ML model that classified chest X-rays as normal or abnormal by using ResNet50 as a base with transfer learning. A contrast enhancement mechanism was implemented to improve performance. After training with a dataset of publicly available chest radiographs, performance metrics were determined with a test set. The ResNet50 base was substituted with deeper architectures (ResNet101/152) and visualization methods used to help determine patterns of inference. Results: Performance metrics were an accuracy of 79%, recall 69%, precision 96%, and area under the curve of 0.9023. Accuracy improved to 82% and recall to 74% with contrast enhancement. When visualization methods were applied and the ratio of pixels used for inference measured, deeper architectures resulted in the model using larger portions of the image for inference as compared to ResNet50. Discussion: The model performed on par with many existing models despite consumer-grade hardware and smaller datasets. Individual models vary thus a single model's explainability may not be generalizable. Therefore, this study varied architecture and studied patterns of inference. With deeper ResNet architectures, the machine used larger portions of the image to make decisions. Conclusion: An example using a custom model showed that AI (Artificial Intelligence) can be accessible on consumer-grade hardware, and it also demonstrated an example of studying themes of ML explainability by varying ResNet architectures. Lay Summary Artificial intelligence (AI) will make a big impact on healthcare. This study creates an example AI application that reads chest X-rays to explore a variety of concepts. First it tried to show that AI work can be accessible to widely available computer hardware and public datasets. Secondly, it showed some new ways of processing chest X-ray data, by increasing the difference between colors in the picture. Thirdly it also explores ways we can better understand how AI's think. This study successfully performed the tasks on a personal computer with datasets from Kaggle (a public website), although real AI work in medicine will require many other factors in addition to these. It found that the special step did improve the AI a little bit. The project tried to look at 3 different AIs with increasing complexity to look at how complexity affects how AIs think. It found that more complex AIs tended to look at larger parts of a chest X-ray to make their final decision when compared to less complex AIs.