Ensembles of Convolutional Neural Networks models for pediatric pneumonia diagnosis

TL;DR

This paper introduces an explainable ensemble CNN approach for pediatric pneumonia diagnosis from chest X-rays, achieving high accuracy on small, low-quality datasets and enhancing interpretability of model decisions.

Contribution

It presents a novel explainability technique based on combining heatmaps from ensemble models and develops new ensemble CNNs that perform well with limited, low-quality data.

Findings

Ensemble models outperform single CNNs and transfer learning in small datasets.

The proposed XAI method improves interpretability of CNN decisions.

High accuracy achieved on pediatric pneumonia X-ray datasets.

Abstract

Pneumonia is a lung infection that causes 15% of childhood mortality, over 800,000 children under five every year, all over the world. This pathology is mainly caused by viruses or bacteria. X-rays imaging analysis is one of the most used methods for pneumonia diagnosis. These clinical images can be analyzed using machine learning methods such as convolutional neural networks (CNN), which learn to extract critical features for the classification. However, the usability of these systems is limited in medicine due to the lack of interpretability, because of these models cannot be used to generate an understandable explanation (from a human-based perspective), about how they have reached those results. Another problem that difficults the impact of this technology is the limited amount of labeled data in many medicine domains. The main contributions of this work are two fold: the first one is the design of a new explainable artificial intelligence (XAI) technique based on combining the individual heatmaps obtained from each model in the ensemble. This allows to overcome the explainability and interpretability problems of the CNN "black boxes", highlighting those areas of the image which are more relevant to generate the classification. The second one is the development of new ensemble deep learning models to classify chest X-rays that allow highly competitive results using small datasets for training. We tested our ensemble model using a small dataset of pediatric X-rays (950 samples) with low quality and anatomical variability (which represents one of the biggest challenges). We also tested other strategies such as single CNNs trained from scratch and transfer learning using CheXNet. Our results show that our ensemble model outperforms these strategies obtaining highly competitive results. Finally, we confirmed the robustness of our approach using another pneumonia diagnosis dataset [1].