Volumetric multicomponent T1ρ relaxation mapping of the human liver under free breathing at 3T

Purpose To develop a 3D sequence for T-1 rho relaxation mapping using radial volumetric encoding (3D-T-1 rho-RAVE) and to evaluate the multi relaxation components in the liver of healthy controls and chronic liver disease (CLD) patients. Methods Fat saturation and T-1 rho preparation modules were followed by a train of gradient-echo acquisitions and T-1 restoration delay. The series of T-1 rho-weighted images were fitted using mono-exponential, bi-exponential, and stretched-exponential models. The repeatability and reproducibility of the proposed technique were evaluated on National Institute of Standards and Technology phantom by calculating the coefficient of variation between test-retest scans on the same scanner and between two different 3T scanners, respectively. Mann-Whitney U-test was performed to assess differences in T-1 rho components among patients (n = 3) and a control group (n = 10). Results The phantom study showed an error of 8.9% and 11.5% in mono T-2 relaxation time measurement relative to the reference on 2 different scanners. The coefficient of variation for test-retest scans performed on the same scanner was 5.7% and 2.4% for scans performed on 2 scanners. The comparison between healthy controls and CLD patients showed a significant difference (P < .05) in mono relaxation time (P = .002), stretched-exponential relaxation parameter (P = .04). The Akaike information criteria C criterion showed 2.53 +/- 0.9% (2.3 +/- 0.3% for CLD) of the voxels are bi-exponential while in 65.3 +/- 5.8% (81.2 +/- 0.06% for CLD) of the liver voxels, the stretched-exponential model was preferred. Conclusion The 3D-T-1 rho-RAVE sequence allows volumetric, multicomponent T-1 rho assessment of the liver during free breathing and can distinguish between healthy volunteers and CLD patients.