Reproducibility of liver R2* quantification for liver iron quantification from cardiac R2* acquisitions

OBJECTIVES: To evaluate the reproducibility of liver R2* measurements between a 2D cardiac ECG-gated and a 3D breath-hold liver CSE-MRI acquisition for liver iron quantification. METHODS: A total of 54 1.5 T MRI exams from 51 subjects (18 women, 36 men, age 35.2 ± 21.8) were included. These included two sub-studies with 23 clinical MRI exams from 19 patients identified retrospectively, 24 participants with known or suspected iron overload, and 7 healthy volunteers acquired prospectively. The 2D cardiac and the 3D liver R2* maps were acquired in the same exam. Either acquisitions were reconstructed using a complex R2* algorithm that accounts for the presence of fat and residual phase errors due to eddy currents. Data were analyzed using colocalized ROIs in the liver. RESULTS: Linear regression analysis demonstrated high Pearson’s correlation and Lin’s concordance coefficient for the overall study and both sub-studies. Bland–Altman analysis also showed good agreement, except for a slight increase of the mean R2* value above ~ 400 s(−1). The Kolmogorow–Smirnow test revealed a non-normal distribution for (R2* 3D–R2* 2D) values from 0 to 600 s(−1) in contrast to the 0–200 s(−1) and 0–400 s(−1) subpopulations. Linear regression analysis showed no relevant differences other than the intercept, likely due to only 7 measurements above 400 s(−1). CONCLUSIONS: The results demonstrate that R2*-measurements in the liver are feasible using 2D cardiac R2* maps compared to 3D liver R2* maps as the reference. Liver R2* may be underestimated for R2* > 400 s(−1) using the 2D cardiac R2* mapping method.