Accelerated free-breathing volumetric liver proton density fat fraction (PDFF) and R 2 ∗ quantification in pediatric...

To evaluate an accelerated free-breathing three-dimensional stack-of-radial MRI technique of liver proton density fat fraction (PDFF) and $\text{R}_2^{\ast }$ quantification on retrospectively undersampled pediatric patient data.

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 $\text{R}_2^{\ast }$ 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 $\text{R}_2^{\ast }$ .

Echo images, PDFF and $\text{R}_2^{\ast }$ 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 $\text{R}_2^{\ast }$ , 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 $\text{R}_2^{\ast }$ . 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 $\text{R}_2^{\ast }$ ROPE. An acceleration factor of 4 and an approximate acquisition time saving of 67% shorter could be achieved.

The proposed method may allow accelerated free-breathing liver PDFF and $\text{R}_2^{\ast }$ mapping in pediatric subjects in approximately 1 min.