Objective
To evaluate an accelerated free-breathing three-dimensional stack-of-radial MRI technique of liver proton density fat fraction (PDFF) and \({\text{R}}_{2}^{*}\) 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 \({\text{R}}_{2}^{*}\) 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 \({\text{R}}_{2}^{*}\) .
Results
Echo images, PDFF and \({\text{R}}_{2}^{*}\) 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 \({\text{R}}_{2}^{*}\) , 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 \({\text{R}}_{2}^{*}\) . 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 \({\text{R}}_{2}^{*}\) 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 \({\text{R}}_{2}^{*}\) mapping in pediatric subjects in approximately 1 min.
