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

PurposeTo 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 (T1w ), proton density fat fraction (PDFF), and R2∗ .MethodsSix-echo bipolar spoiled gradient echo readouts following inversion recovery preparation was performed to generate T1 , water/fat, and R2∗ 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 T1w quantification, followed by the estimation of R2∗ 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.ResultsMT-ME produced high-quality, coregistered T1 , T1w , PDFF, and R2∗ maps with good intrasession repeatability and substantial agreement with references on phantom and human studies. The intra-class coefficients of T1 , T1w , PDFF, and R2∗ 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 R2∗ 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 T1w was independent to PDFF (R = -0.029, P = .904).ConclusionThe proposed MT-ME technique quantifies T1 , T1w , PDFF, and R2∗ simultaneously and is clinically promising for the comprehensive characterization of liver tissue properties