Free-breathing multitasking multi-echo MRI for whole-liver water-specific T₁, proton density fat fraction, and R2∗ quantification

Purpose: To develop a 3D multitasking multi-echo (MT-ME) technique for the comprehensive characterization of liver tissues with 5-min free-breathing acquisition; whole-liver coverage; a spatial resolution of 1.5 × 1.5 × 6 mm³; and simultaneous quantification of T₁, water-specific T₁ (T_1w), proton density fat fraction (PDFF), and (Formula presented.). Methods: Six-echo bipolar spoiled gradient echo readouts following inversion recovery preparation was performed to generate T₁, water/fat, and (Formula presented.) contrast. MR multitasking was used to reconstruct the MT-ME images with 3 spatial dimensions: 1 T₁ recovery dimension, 1 multi-echo dimension, and 1 respiratory dimension. A basis function–based approach was developed for T_1w quantification, followed by the estimation of (Formula presented.) and T₁-corrected PDFF. The intrasession repeatability and agreement against references of MT-ME measurements were tested on a phantom and 15 clinically healthy subjects. In addition, 4 patients with confirmed liver diseases were recruited, and the agreement between MT-ME measurements and references was assessed. Results: MT-ME produced high-quality, coregistered T₁, T_1w, PDFF, and (Formula presented.) maps with good intrasession repeatability and substantial agreement with references on phantom and human studies. The intra-class coefficients of T₁, T_1w, PDFF, and (Formula presented.) from the repeat MT-ME measurements on clinically healthy subjects were 0.989, 0.990, 0.999, and 0.988, respectively. The intra-class coefficients of T₁, PDFF, and (Formula presented.) between the MT-ME and reference measurements were 0.924, 0.987, and 0.975 in healthy subjects and 0.980, 0.999, and 0.998 in patients. The T_1w was independent to PDFF (R = −0.029, P =.904). Conclusion: The proposed MT-ME technique quantifies T₁, T_1w, PDFF, and (Formula presented.) simultaneously and is clinically promising for the comprehensive characterization of liver tissue properties.