Masked Attention as a Mechanism for Improving Interpretability of Vision Transformers

TL;DR

This paper introduces a masking technique in Vision Transformers that filters out background regions, enhancing interpretability and robustness in medical image analysis without sacrificing accuracy.

Contribution

It proposes a novel background masking method within the attention mechanism of Vision Transformers, improving interpretability in histopathology applications.

Findings

Achieves comparable accuracy to standard models.

Produces more accurate and clinically meaningful attention heatmaps.

Enhances model robustness by ignoring non-informative background regions.

Abstract

Vision Transformers are at the heart of the current surge of interest in foundation models for histopathology. They process images by breaking them into smaller patches following a regular grid, regardless of their content. Yet, not all parts of an image are equally relevant for its understanding. This is particularly true in computational pathology where background is completely non-informative and may introduce artefacts that could mislead predictions. To address this issue, we propose a novel method that explicitly masks background in Vision Transformers' attention mechanism. This ensures tokens corresponding to background patches do not contribute to the final image representation, thereby improving model robustness and interpretability. We validate our approach using prostate cancer grading from whole-slide images as a case study. Our results demonstrate that it achieves comparable performance with plain self-attention while providing more accurate and clinically meaningful attention heatmaps.