Introduction

Liver function is a key factor that can help predict the clinical outcome in patients with cirrhosis (1, 2). Since cumulative data have shown liver function is heterogeneous over the liver, imaging-based liver function estimation using gadoxetic acid-enhanced MRI would be beneficial for these patients. There have been various attempts to estimate liver function using MRI, and one of them is hepatocyte fraction measurement (3). Thus, the purpose of this study is to determine whether hepatocyte fraction shows significant correlation with indocyanine green retention test (ICG R15) which is commonly used for estimating liver function quantitatively in critical situation.

Methods

This prospective ongoing study was approved by our institutional review board, and informed consent was obtained from all patients. From Aug 2016, a total of 33 patients with chronic liver disease (M:F=28:5, mean age 59.8±9.2 years) were enrolled and underwent gadoxetic acid-enhanced liver MRI followed by ICG R15 test. A standard dose of gadoxetic acid (0.025mmol/kg) was intravenously injected. Fat quantification map was obtained using multi-echo Dixon method before contrast media injection. In addition, T1 map of the liver using Look-Locker sequence was obtained before contrast (preT1 map) media injection and 10 minutes (post T1 map) after contrast media injection using following scan parameters: T1-TFE, TR/TE = 7/1.7msec, FA=7º, acceleration factor of 2, shot interval = 5msec. Pre- and post-contrast T1 values (msec), difference of them (ΔT1), hepatocyte fraction and rate of hepatocyte uptake (K) were calculated using dedicated off-line software according to previous study schemes (Fig 1).

Results and discussion

There were 87.9% (29/33) patients with chronic liver disease or Child-Pugh A, and 12.1% (4/33) patients were Child-Pugh class B. There were significant differences of ICG R15 (18.7±14.9% vs. 62.6±17.7%, P<0.0001), hepatocyte fraction (66.4±8.5%, 52.7±11.6%, P<0.007), K (21.8±9.5 vs. 8.8±4.0, P=0.01) and post T1 (339.7±82.4 msec vs. 496.3±119.2 msec, P=0.002) between two groups (Fig 2). However, ΔT1 and preT1 did not show significant difference (P=0.27, P=0.31). Hepatocyte fraction and K showed a significant negative correlation with ICG R15 (r=-0.50 [95% CI: -0.72, -0.19], and -0.68[95% CI: -0.83, -0.45]), as well as Child-Pugh scores (r=-0.47 [-0.7, -0.15], -0.48[-0.7, -0.16]). Especially hepatocyte fraction and ICG R15 showed heterogeneous distribution in compensated cirrhosis patients (Child A) (Figs 2, 3). Since identifying high-risk group of hepatic decompensation is clinically important for patient management, it could be clinically valuable information.

Conclusion

Hepatocyte fraction and uptake ratio derived from gadoxetic acid enhanced liver MRI showed a significantly negative correlation with ICG R15, which may suggest the potential capability of gadoxetic acid-enhanced MRI as a quantitative marker of liver function.

Acknowledgements

Supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education (2013R1A1A2A10066037).