T2^* Mapping from Multi-Echo Dixon Sequence on Gadoxetic Acid-Enhanced Magnetic Resonance Imaging for the Hepatic Fat Quantification: Can It Be Used for Hepatic Function Assessment?

Objective: To evaluate the diagnostic value of $T2^*$ mapping using 3D multi-echo Dixon gradient echo acquisition on gadoxetic acid-enhanced liver magnetic resonance imaging (MRI) as a tool to evaluate hepatic function. Materials and Methods: This retrospective study was approved by the IRB and the requirement of informed consent was waived. 242 patients who underwent liver MRIs, including 3D multi-echo Dixon fast gradient-recalled echo (GRE) sequence at 3T, before and after administration of gadoxetic acid, were included. Based on clinico-laboratory manifestation, the patients were classified as having normal liver function (NLF, n = 50), mild liver damage (MLD, n = 143), or severe liver damage (SLD, n = 30). The 3D multi-echo Dixon GRE sequence was obtained before, and 10 minutes after, gadoxetic acid administration. Pre- and post-contrast $T2^*$ values, as well as $T2^*$ reduction rates, were measured from $T2^*$ maps, and compared among the three groups. Results: There was a significant difference in $T2^*$ reduction rates between the NLF and SLD groups ($-0.2{\pm}4.9%$ vs. $5.0{\pm}6.9%$, p = 0.002), and between the MLD and SLD groups ($3.2{\pm}6.0%$ vs. $5.0{\pm}6.9%$, p = 0.003). However, there was no significant difference in both the pre- and post-contrast $T2^*$ values among different liver function groups (p = 0.735 and 0.131, respectively). A receiver operating characteristic (ROC) curve analysis showed that the area under the ROC curve for using $T2^*$ reduction rates to differentiate the SLD group from the NLF group was 0.74 (95% confidence interval: 0.63-0.83). Conclusion: Incorporation of $T2^*$ mapping using 3D multi-echo Dixon GRE sequence in gadoxetic acid-enhanced liver MRI protocol may provide supplemental information for liver function deterioration in patients with SLD.