Highly efficient non-rigid registration in k-space with application to cardiac Magnetic Resonance Imaging

TL;DR

This paper introduces LAPANet, a deep learning framework that estimates non-rigid motion directly from accelerated MRI k-space data, achieving high accuracy and temporal resolution for real-time cardiac imaging.

Contribution

The novel LAPANet approach models non-rigid motion as local translations directly in k-space, outperforming existing methods in accuracy and speed for dynamic MRI applications.

Findings

LAPANet achieves superior accuracy over traditional and deep learning methods.

It can operate effectively with minimal data, as few as 2 lines/frame.

High temporal resolution (<5 ms) enables real-time motion tracking.

Abstract

In Magnetic Resonance Imaging (MRI), high temporal-resolved motion can be useful for image acquisition and reconstruction, MR-guided radiotherapy, dynamic contrast-enhancement, flow and perfusion imaging, and functional assessment of motion patterns in cardiovascular, abdominal, peristaltic, fetal, or musculoskeletal imaging. Conventionally, these motion estimates are derived through image-based registration, a particularly challenging task for complex motion patterns and high dynamic resolution. The accelerated scans in such applications result in imaging artifacts that compromise the motion estimation. In this work, we propose a novel self-supervised deep learning-based framework, dubbed the Local-All Pass Attention Network (LAPANet), for non-rigid motion estimation directly from the acquired accelerated Fourier space, i.e. k-space. The proposed approach models non-rigid motion as the cumulative sum of local translational displacements, following the Local All-Pass (LAP) registration technique. LAPANet was evaluated on cardiac motion estimation across various sampling trajectories and acceleration rates. Our results demonstrate superior accuracy compared to prior conventional and deep learning-based registration methods, accommodating as few as 2 lines/frame in a Cartesian trajectory and 3 spokes/frame in a non-Cartesian trajectory. The achieved high temporal resolution (less than 5 ms) for non-rigid motion opens new avenues for motion detection, tracking and correction in dynamic and real-time MRI applications.