Tagged-Informed Prior for Motion Quantification in Cine CMR Using Implicit Neural Representations

Laura Alvarez Florez, Soufiane Ben Haddou, Fleur V. Y. Tjong, Ivana Isgum

Keywords: Cardiac MRI, Tagged CMR, Implicit Neural Representations, Image Registration, Cardiac Motion Quantification, Prior Initialization

TL;DR: We use tagged CMR to build a population motion prior for INR-based cine CMR registration.

Abstract: Accurate quantification of myocardial motion from cine cardiac magnetic resonance (CMR) is essential for assessing cardiac function. Although tagged CMR provides high-fidelity measurements of myocardial deformation, its longer acquisition time limits routine clinical use, making cine CMR motion estimation the more widely applicable approach. Implicit neural representations (INRs) offer a promising framework for cine-based motion estimation by modelling cardiac motion as a continuous spatiotemporal function. However, they require subject-specific optimisation and are sensitive to initialization, leading to slow convergence. Furthermore, optimisation from random initialization can lead to large number of solutions that may not guarantee biomechanically plausible motion. To address these limitations, we propose a strategy to improve and accelerate INR-based registration of cine CMR by leveraging a population-level prior derived from tagged CMR data. First, we train subject-specific INRs on the tagged-cine dataset to encode characteristic myocardial deformation patterns. Second, we aggregate their parameters across subjects to form a tagged-informed population prior. Third, we use this prior initialization to warm-start the optimization of cine INRs. The resulting prior provides a physiologically meaningful starting point for cine-only INR optimisation, reducing the search space and promoting more realistic cardiac motion. We develop and test the method on the UK Biobank. Compared with standard initialization, the proposed prior enables the INR to reach near-optimal performance using only half as many optimisation steps, achieving a 4% improvement in Dice and a 15% reduction in Hausdorff distance. These gains also translate to another test set of 855 subjects from a different institution, encompassing different pathologies, where the prior yields smoother and more physiologically plausible strain curves. To support reproducibility, upon publication and approval, we will publicly release the prior weights and accompanying code.

Primary Subject Area: Application: Cardiology

Secondary Subject Area: Image Registration

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Submission Number: 161