2024/9 - Trajectory correction enables free-running chemical shift encoded imaging for accurate cardiac proton-density fat fraction quantification at 3T [Journal Club]-September JCMR Journal Club

Video Transcription

Video Summary

The transcript is from a JCMR Journal Club session focused on a recent paper about free-running, trajectory-corrected chemical shift-encoded cardiac MRI for epicardial adipose tissue (EAT) fat-fraction mapping. The presenters explained that EAT is an important cardiovascular risk marker and that its composition, not just volume, may reflect metabolic health.<br /><br />They described a 3D, free-breathing, multi-echo cardiac sequence that reconstructs cardiac and respiratory phases from self-navigation data, then uses fat-water separation to generate fat fraction and R2* maps. A key challenge was gradient imperfections, especially in bipolar readouts, which can cause trajectory errors and fat-water swaps. The team showed that gradient impulse response function (GIRF) correction substantially improves image quality and quantitative accuracy.<br /><br />Simulations and in vivo data suggested bipolar acquisition with GIRF correction was superior to monopolar imaging for accurate fat fraction estimation. The method enabled clearer separation of epicardial and subcutaneous fat, and preliminary results in healthy volunteers and diabetic patients showed lower fat fraction in epicardial fat than in subcutaneous fat.<br /><br />Limitations included long scan and reconstruction times, imperfect R2* robustness, and the need for further validation. The discussion covered fat spectral modeling, spatial and temporal resolution, 1.5T feasibility, reproducibility, and the role of motion correction and 3D imaging for future clinical use.

Keywords

epicardial adipose tissue

cardiac MRI

fat fraction mapping

chemical shift encoding

gradient impulse response function

bipolar readout

motion correction

R2* mapping

free-breathing 3D imaging