Multi-Contrast MRI Arbitrary-Scale Super-Resolution via Dynamic Implicit Network

Multi-contrast MRI super-resolution (SR) aims to restore high-resolution target image from low-resolution one, where reference image from another contrast is used to promote this task. To better meet clinical needs, current studies mainly focus on developing arbitrary-scale MRI SR solutions rather than fixed-scale ones. However, existing arbitrary-scale SR methods still suffer from the following two issues: 1) They typically rely on fixed convolutions to learn multi-contrast features, struggling to handle the feature transformations under varying scales and input image pairs, thus limiting their representation ability. 2) They simply combine the multi-contrast features as prior information, failing to fully exploit the complementary information in the texture-rich reference images. To address these issues, we propose a Dynamic Implicit Network (DINet) for multi-contrast MRI arbitrary-scale SR. DINet offers several key advantages. First, the scale-adaptive dynamic convolution facilitates dynamic feature learning based on scale factors and input image pairs, significantly enhancing the representation ability of multi-contrast features. Second, the dual-branch implicit attention enables arbitrary-scale upsampling of MR images through implicit neural representation. Following this, we propose the modulation-then-fusion block to adaptively align and fuse multi-contrast features, effectively incorporating complementary details from reference images into the target images. By jointly combining the above-mentioned modules, our proposed DINet achieves superior MRI SR performance at arbitrary scales. Extensive experiments on three datasets demonstrate that DINet significantly outperforms state-of-the-art methods, highlighting its potential for clinical applications. The code is available at https://github.com/weijinbao1998/DINet.