FINDER: Zero-Shot Field-Integrated Network for Distortion-free EPI Reconstruction in Diffusion MRI

TL;DR

FINDER is a novel zero-shot, scan-specific deep learning framework that jointly reconstructs distortion-free diffusion MRI images and estimates the $B_{0}$ field map, improving geometric fidelity without prior training.

Contribution

The paper introduces FINDER, a physics-guided unrolled network with implicit neural representations for joint MRI reconstruction and distortion correction in a self-supervised manner.

Findings

FINDER outperforms state-of-the-art methods in geometric fidelity.

FINDER effectively disentangles susceptibility distortions from anatomical structures.

FINDER achieves high-quality diffusion MRI reconstruction without prior training.

Abstract

Echo-planar imaging (EPI) remains the cornerstone of diffusion MRI, but it is prone to severe geometric distortions due to its rapid sampling scheme that renders the sequence highly sensitive to $B_{0}$ field inhomogeneities. While deep learning has helped improve MRI reconstruction, integrating robust geometric distortion correction into a self-supervised framework remains an unmet need. To address this, we present FINDER (Field-Integrated Network for Distortion-free EPI Reconstruction), a novel zero-shot, scan-specific framework that reformulates reconstruction as a joint optimization of the underlying image and the $B_{0}$ field map. Specifically, we employ a physics-guided unrolled network that integrates dual-domain denoisers and virtual coil extensions to enforce robust data consistency. This is coupled with an Implicit Neural Representation (INR) conditioned on spatial coordinates and latent image features to model the off-resonance field as a continuous, differentiable function. Employing an alternating minimization strategy, FINDER synergistically updates the reconstruction network and the field map, effectively disentangling susceptibility-induced geometric distortions from anatomical structures. Experimental results demonstrate that FINDER achieves superior geometric fidelity and image quality compared to state-of-the-art baselines, offering a robust solution for high-quality diffusion imaging.