Liver T1ρ MRI measurement in healthy human subjects at 3 T: a preliminary study with a two-dimensional fast-field echo sequence

Objectives: The aim of this study was to explore the technical feasibility of T-1 rho MRI for the liver, and to determine the normal range of liver T-1 rho in healthy subjects at clinical 3 T. Methods: There were 15 healthy volunteers. Three representative axial slices were selected to cut through the upper, middle and lower liver. A rotary echo spin-lock pulse was implemented in a two-dimensional fast-field echo sequence. Spin-lock frequency was 500 Hz, and the spin-lock times of 1, 10, 20, 30, 40 and 50 ms were used for T-1 rho mapping. The images were acquired slice by slice during breath-holding. Regions of interest (ROIs; n=5) were manually placed on each slice of the liver parenchyma region, excluding artefacts and vessels. The mean value of these ROIs (n=15) was regarded as the liver T-1 rho value for the subject. Six subjects were scanned once at fasting status; six subjects were scanned once 2 h post meal; three subjects were scanned twice at fasting status; and seven subjects were scanned twice 2 h post meal. Results: When two readers measured the same 10 data sets, the interreader reproducibility (ICC: intraclass correlation coefficient) was 0.955. With the 10 subjects scanned twice, the ICC for scan-rescan reproducibility was 0.764. There was no significant difference for the liver T-1 rho value at the fasting status (43.08 +/- 1.41 ms) and post-meal status (42.97 +/- 2.38 ms, p=0.867). Pooling together all the 32 scans in this study, the normal liver T-1 rho value ranged from 38.6 to 48.3 ms (mean 43.0 ms, median 42.6 ms). Conclusion: It is feasible to obtain consistent liver T-1 rho measurement for human subjects at 3 T.