Motion-robust, high-SNR liver fat quantification using a 2D sequential acquisition with a variable flip angle...

Area of Science:

• Magnetic Resonance Imaging
• Medical Physics
• Biomarker Quantification

Background:

• Chemical shift encoded (CSE)-MRI quantifies liver fat via proton-density fat fraction (PDFF).
• Conventional 3D Cartesian CSE-MRI requires breath-holding, limiting its clinical utility.
• Existing 2D methods are motion-robust but suffer from low signal-to-noise ratio (SNR).

Purpose of the Study:

• To develop a novel free-breathing 2D Cartesian sequential CSE-MRI method.
• To achieve accurate liver fat quantification with high SNR and minimal bias.
• To implement a variable flip angle (VFA) approach with centric phase encoding (VFA-centric).

Main Methods:

• Numerical simulations were used for VFA schedule design and method evaluation.
• Phantom and in vivo imaging (n=35) were performed at 3T.
• PDFF maps were estimated from multi-echo images; PDFF standard deviation served as an SNR surrogate.

Main Results:

• The VFA-centric method demonstrated higher SNR and minimal bias in simulations and phantom experiments.
• A high correlation ($$=0.998) was observed between VFA-centric PDFF and reference PDFF in vivo.
• VFA-centric achieved superior SNR (1.5% std dev) compared to reference acquisition (3.3% std dev, P < .001).

Conclusions:

• The developed VFA-centric method provides motion robustness and high SNR for liver fat quantification.
• This free-breathing 2D CSE-MRI technique overcomes limitations of previous 2D sequential methods.
• The method offers accurate PDFF measurement with low bias and minimal blurring.