Abstract Objective To evaluate an accelerated free-breathing three-dimensional stack-of-radial MRI technique of liver proton density fat fraction (PDFF) and R₂^* R 2 ∗ quantification on retrospectively undersampled pediatric patient data. Methods A newly developed compressed sensing reconstruction with multidimensional regularization was evaluated on undersampled data in 21 clinical pediatric subjects at 1. 5 T with respect to the reference-standard self-gating reconstruction on oversampled data (700 radial views per slice). PDFF and R₂^* R 2 ∗ maps were calculated using the proposed method with fully sampled and undersampled radial views (352 and 176) and compared to reference-standard results using Bland-Altman analysis (reported as mean difference; lower, upper limits of agreement). Practical equivalence was evaluated using Bayesian posterior analysis with region of practical equivalence (ROPE) at ± 3% for PDFF and ± 10 s −1 for R₂^* R 2 ∗. Results Echo images, PDFF and R₂^* R 2 ∗ maps reconstructed using the proposed method had reduced image artifacts. Bland-Altman plots showed that the proposed method using 176 views had lower biases, -0. 7;-2. 4, 1. 0% for PDFF and -5. 3;-25. 5, 14. 9 s −1 for R₂^* R 2 ∗, compared to the reference method using 352 views: 0. 8; -0. 6, 2. 1% for PDFF and -9. 2;-51. 9, 33. 4 s −1 for R₂^* R 2 ∗. Bayesian posterior analysis revealed that our proposed method using 176 views was practically equivalent to the reference method using 700 views with 100% within the PDFF ROPE and with 98. 25% within the R₂^* R 2 ∗ ROPE. An acceleration factor of 4 and an approximate acquisition time saving of 67% shorter could be achieved. Conclusion The proposed method may allow accelerated free-breathing liver PDFF and R₂^* R 2 ∗ mapping in pediatric subjects in approximately 1 min.
Zhong et al. (Thu,) studied this question.