Free-breathing multitasking multi-echo MRI for whole-liver water-specific T1, proton density fat fraction, and R2* quantification
Nan Wang, Tianle Cao, Fei Han, Yibin Xie, Xiaodong Zhong, Sen Ma, Alan Kwan, Zhaoyang Fan, Hui Han,Xiaoming Bi, Mazen Noureddin, Vibhas Deshpande, Anthony G. Christodoulou, Debiao Li
Abstract
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 (T1w), proton density fat fraction (PDFF), and 
.
Methods
Six-echo bipolar spoiled gradient echo readouts following inversion recovery preparation was performed to generate T1, water/fat, and 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 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, T1w, PDFF, and maps with good intrasession repeatability and substantial agreement with references on phantom and human studies. The intra-class coefficients of T1, T1w, PDFF, and 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 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).
Conclusion
The proposed MT-ME technique quantifies T1, T1w, PDFF, and simultaneously and is clinically promising for the comprehensive characterization of liver tissue properties.