LongFormer: Longitudinal Transformer for Alzheimer’s Disease Classification with Structural MRIs

Structural magnetic resonance imaging (sMRI), especially longitudinal sMRI, is often used to monitor and capture disease progression during the clinical diagnosis of Alzheimer's Disease (AD). However, current methods neglect AD’s progressive nature and have mostly relied on a single image for recognizing AD. In this paper, we consider the problem of leveraging the longitudinal MRIs of a subject for AD classification. To address the challenges of missing data, data demand, and subtle changes over time in learning longitudinal 3D MRIs, we propose a novel model LongFormer, which is a hybrid 3D CNN and transformer design to learn from image and longitudinal flow pairs. Our model can fully leverage all images in a dataset and effectively fuse spatiotemporal features for classification. We evaluate our model on three datasets, i.e., ADNI, OASIS, and AIBL, and compare it to eight baseline algorithms. Our proposed LongFormer achieves state-of-the-art performance in classifying AD and NC subjects from all three public datasets. Our source code is available online at https://github.com/Qybc/LongFormer.