DBCE : A Saliency Method for Medical Deep Learning Through Anatomically-Consistent Free-Form Deformations
Joshua Peters, Léo Lebrat, Rodrigo Santa Cruz, Aaron Nicolson, Gregg Belous, Salamata Konate, Parnesh Raniga, Vincent Doré, Pierrick Bourgeat, Jürgen Fripp, Clinton Fookes, Olivier Salvado · 2023 IEEE/CVF Winter Conference on Applications of Computer Vision (WACV) · 2023
Deep learning models are powerful tools for addressing challenging medical imaging problems. However, for an ever-growing range of applications, interpreting a model’s prediction remains non-trivial. Understanding decisions made by black-box algorithms is critical, and assessing their fairness and susceptibility to bias is a key step towards healthcare deployment. In this paper, we propose DBCE (Deformation Based Counterfactual Explainability). We optimise a diffeomorphic transformation that deforms a given input image to change the prediction of the model. This provides anatomically meaningful saliency maps indicating tissue atrophy and expansion, which can be easily interpreted by clinicians. In our test case, DBCE replicates the transition of a patient from healthy control (HC) to Alzheimer’s disease (AD). We benchmark DBCE against three commonly used saliency methods. We show that it provides more meaningful saliency maps when applied to one subject and disease-consistent atrophy patterns when used over a larger cohort. In addition, our method fulfils a recent sanity check and is repeatable for different model initialisations in contrast to classical sensitivity-based methods.