Explainable artificial intelligence-based classification of asthma and COPD from xenon-129 ventilation magnetic resonance imaging

Diagnosis of asthma and/or COPD is challenging due to overlapping clinical and physiological characteristics; however, due to varying treatment recommendations, determining the correct diagnosis is vital to clinical care. Hyperpolarised xenon-129 ventilation (¹²⁹Xe)-magnetic resonance imaging (MRI) provides high spatial resolution three-dimensional images of gas distribution within the lungs. Recently, artificial intelligence (AI)-based models have successfully classified pulmonary pathologies via medical images, but due to their black-box nature, clinical application is challenging. Here, we aim to develop an explainable AI framework to classify patients with asthma and/or COPD using ¹²⁹Xe-MRI alone.

¹²⁹Xe-MRI from 207 patients with asthma and/or COPD were classified using a vision transformer (ViT) and a convolutional neural network (CNN). Regional visualisations of areas of importance (AOIs) associated with each diagnosis were generated. Regional patterns were investigated to develop a shape-based metric which quantified asthma-like and COPD-like features.

The ViT accurately classified asthma and/or COPD patients in 83% (n=25/30) of cases (area under the curve (AUC) 0.86, F₁ score 0.82), outperforming the CNN (AUC 0.71, F₁ score 0.62). Patients with asthma had more diffuse, elongated AOIs associated with disease grouping while patients with COPD had more focal, spherical AOIs. The proposed sphericity score weakly correlated with conventional lung function metrics in clinically understandable ways. When applied to patients with overlapping features of asthma and COPD (asthma+COPD), the classification framework informed the prevalence and regional distribution of asthma-like and COPD-like features.

Explainable AI classification of ¹²⁹Xe-MRI could facilitate diagnosis of patients with asthma and/or COPD, including determining the prevalence of asthma-like or COPD-like features in patients with asthma+COPD, potentially informing management and treatment.