Magnetic resonance imaging · 2025
Quantitative proton density fat-fraction at 9.4 T using fast spin echo and asymmetric multi-echo gradient-echo pulse sequences.
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Kořínek Radim, Krátká Lucie, Starčuk Zenon
Аннотация
PURPOSE: Quantifying proton density fat fraction (PDFF) in small abdominal organs is challenging due to low T1/T2 contrast and susceptibility artifacts. We develop a hybrid 7-echo CSE-MRI sequence with arbitrary echo spacing, inspired by GRASE-type imaging, aiming for distortion-free PDFF mapping in small animals. The method is designed to be comparable to established conventional methods, with potential for increased robustness.
METHODS: We developed a Fast Spin Echo Asymmetric Bipolar Multi-Gradient Echo (FSE-AbMGE) sequence by integrating a fast spin-echo readout with an asymmetrically placed bipolar multi-echo gradient-echo train. The sequence was implemented at 9.4 T and combined with robust phase unwrapping and water-fat reconstruction algorithms using full fat spectral modeling. Validation was performed using phantoms with known PDFF values (0-22 %) and in vivo experiments on several female mice (n = 2). Reference PDFF values were obtained using single-voxel 1H-MRS.
RESULTS: The proposed method enabled high-resolution PDFF mapping with minimal chemical shift and susceptibility artifacts. Phantom experiments showed strong agreement with both spectroscopic and ground truth values (R2 > 0.98, p < 0.001). The method was also tested in vivo, demonstrating robust water-fat separation and quantification.
CONCLUSION: The FSE-AbMGE sequence is well-suited for accurate abdominal fat quantification in small animals. While additional validation is needed, especially in reproducibility and broader biological settings, the method shows promise for high-field fat quantification and may offer a framework adaptable to lower-field pre-clinical applications.
METHODS: We developed a Fast Spin Echo Asymmetric Bipolar Multi-Gradient Echo (FSE-AbMGE) sequence by integrating a fast spin-echo readout with an asymmetrically placed bipolar multi-echo gradient-echo train. The sequence was implemented at 9.4 T and combined with robust phase unwrapping and water-fat reconstruction algorithms using full fat spectral modeling. Validation was performed using phantoms with known PDFF values (0-22 %) and in vivo experiments on several female mice (n = 2). Reference PDFF values were obtained using single-voxel 1H-MRS.
RESULTS: The proposed method enabled high-resolution PDFF mapping with minimal chemical shift and susceptibility artifacts. Phantom experiments showed strong agreement with both spectroscopic and ground truth values (R2 > 0.98, p < 0.001). The method was also tested in vivo, demonstrating robust water-fat separation and quantification.
CONCLUSION: The FSE-AbMGE sequence is well-suited for accurate abdominal fat quantification in small animals. While additional validation is needed, especially in reproducibility and broader biological settings, the method shows promise for high-field fat quantification and may offer a framework adaptable to lower-field pre-clinical applications.