Spatial-Angular Representation Learning for High-Fidelity Continuous Super-Resolution in Diffusion MRI

TL;DR

This paper introduces SARL-dMRI, a novel framework that leverages implicit neural representations and spherical harmonics to achieve high-fidelity, continuous super-resolution in diffusion MRI, enhancing microstructural detail recovery.

Contribution

SARL-dMRI is the first method to jointly model continuous spatial and angular representations for super-resolution in dMRI, integrating data-fidelity and wavelet-based loss for improved image quality.

Findings

Significantly improves resolution over state-of-the-art methods.

Enhances microstructural parameter estimation accuracy.

Maintains stable performance under 45× downsampling.

Abstract

Diffusion magnetic resonance imaging (dMRI) often suffers from low spatial and angular resolution due to inherent limitations in imaging hardware and system noise, adversely affecting the accurate estimation of microstructural parameters with fine anatomical details. Deep learning-based super-resolution techniques have shown promise in enhancing dMRI resolution without increasing acquisition time. However, most existing methods are confined to either spatial or angular super-resolution, limiting their effectiveness in capturing detailed microstructural features. Furthermore, traditional pixel-wise loss functions struggle to recover intricate image details essential for high-resolution reconstruction. To address these challenges, we propose SARL-dMRI, a novel Spatial-Angular Representation Learning framework for high-fidelity, continuous super-resolution in dMRI. SARL-dMRI explores implicit neural representations and spherical harmonics to model continuous spatial and angular representations, simultaneously enhancing both spatial and angular resolution while improving microstructural parameter estimation accuracy. To further preserve image fidelity, a data-fidelity module and wavelet-based frequency loss are introduced, ensuring the super-resolved images remain consistent with the original input and retain fine details. Extensive experiments demonstrate that, compared to five other state-of-the-art methods, our method significantly enhances dMRI data resolution, improves the accuracy of microstructural parameter estimation, and provides better generalization capabilities. It maintains stable performance even under a 45$\times$ downsampling factor.