TR-TransGAN: Temporal Recurrent Transformer Generative Adversarial Network for Longitudinal MRI Dataset Expansion

Longitudinal magnetic resonance imaging (MRI) datasets have important implications for the study of degenerative diseases because such datasets have data from multiple points in time to track disease progression. However, longitudinal datasets are often incomplete due to unexpected quits of patients. In previous work, we proposed an augmentation method temporal recurrent generative adversarial network (TR-GAN) that can complement missing session data of MRI datasets. TR-GAN uses a simple U-Net as a generator, which limits its performance. Transformers have had great success in the research of computer vision and this article attempts to introduce it into longitudinal dataset completion tasks. The multihead attention mechanism in transformer has huge memory requirements, and it is difficult to train 3-D MRI data on graphics processing units (GPUs) with small memory. To build a memory-friendly transformer-based generator, we introduce a Hilbert transform module (HTM) to convert 3-D data to 2-D data that preserves locality fairly well. To make up for the insufficiency of convolutional neural network (CNN)-based models that are difficult to establish long-range dependencies, we propose an Swin transformer-based up/down sampling module (STU/STD) module that combines the Swin transformer module and CNN module to capture global and local information simultaneously. Extensive experiments show that our model can reduce mean squared error (MMSE) by at least 7.16% compared to the previous state-of-the-art method.