Brightness-Invariant Tracking Estimation in Tagged MRI

TL;DR

This paper introduces BRITE, a novel brightness-invariant method for tracking tissue motion in tagged MRI that effectively handles brightness changes and tag fading, improving accuracy over existing techniques.

Contribution

BRITE combines denoising diffusion models and physics-informed neural networks to disentangle anatomy from tags and estimate motion robustly in brightness-variable MRI data.

Findings

BRITE outperforms state-of-the-art methods in motion and strain estimation.

The method demonstrates robustness to tag fading and brightness variations.

Validated on gel phantom images with various imaging parameters.

Abstract

Magnetic resonance (MR) tagging is an imaging technique for noninvasively tracking tissue motion in vivo by creating a visible pattern of magnetization saturation (tags) that deforms with the tissue. Due to longitudinal relaxation and progression to steady-state, the tags and tissue brightnesses change over time, which makes tracking with optical flow methods error-prone. Although Fourier methods can alleviate these problems, they are also sensitive to brightness changes as well as spectral spreading due to motion. To address these problems, we introduce the brightness-invariant tracking estimation (BRITE) technique for tagged MRI. BRITE disentangles the anatomy from the tag pattern in the observed tagged image sequence and simultaneously estimates the Lagrangian motion. The inherent ill-posedness of this problem is addressed by leveraging the expressive power of denoising diffusion probabilistic models to represent the probabilistic distribution of the underlying anatomy and the flexibility of physics-informed neural networks to estimate biologically-plausible motion. A set of tagged MR images of a gel phantom was acquired with various tag periods and imaging flip angles to demonstrate the impact of brightness variations and to validate our method. The results show that BRITE achieves more accurate motion and strain estimates as compared to other state of the art methods, while also being resistant to tag fading.