Mind the Gap: Promoting Missing Modality Brain Tumor Segmentation with Alignment

TL;DR

This paper introduces a novel alignment-based knowledge distillation method for brain tumor segmentation that effectively handles missing MRI modalities by aligning features to a distribution anchor, improving performance across different models.

Contribution

It proposes a new training paradigm that aligns latent features across modalities to a distribution anchor, ensuring invariant representations and reducing modality gaps, with theoretical proof of effectiveness.

Findings

Achieves an average 1.75 dice score improvement.

Enables invariant feature representations across modalities.

Produces a teacher model with narrowed modality gaps.

Abstract

Brain tumor segmentation is often based on multiple magnetic resonance imaging (MRI). However, in clinical practice, certain modalities of MRI may be missing, which presents an even more difficult scenario. To cope with this challenge, knowledge distillation has emerged as one promising strategy. However, recent efforts typically overlook the modality gaps and thus fail to learn invariant feature representations across different modalities. Such drawback consequently leads to limited performance for both teachers and students. To ameliorate these problems, in this paper, we propose a novel paradigm that aligns latent features of involved modalities to a well-defined distribution anchor. As a major contribution, we prove that our novel training paradigm ensures a tight evidence lower bound, thus theoretically certifying its effectiveness. Extensive experiments on different backbones validate that the proposed paradigm can enable invariant feature representations and produce a teacher with narrowed modality gaps. This further offers superior guidance for missing modality students, achieving an average improvement of 1.75 on dice score.