Variational Visible Layers: A Practical Framework for Uncertainty Estimation

Uncertainty estimation is critical for reliable decision-making in medical imaging. State-of-the-art uncertainty methods require significant computational overhead and complex modeling. In this work, we present and explore a simple, effective approach to incorporating Bayesian uncertainty into deterministic networks by replacing the first and/or last layer (visible layers) with their variational Bayesian counterpart. This lightweight modification enables uncertainty quantification through mean-field variational estimation, making it practical for real-world medical applications. We evaluate the methods on ISIC and LIDC-IDRI for the segmentation task and DermaMNIST and ChestMNIST for the classification task using post-hoc and jointly-trained visible layers. We demonstrate that variational visible layers enable uncertainty-based failure detection for both in-distribution and near-out-of-distribution samples, preserving task performance while reducing the number of variational parameters required for Bayesian estimation. We provide an easy-to-implement solution for integrating uncertainty estimation into existing pipelines.