Noninvasive Assessment of Fat and Iron Deposition in the Liver by PDFF and T2* Measurement Using the 6-Point DIXON Method

Background: The gold standard procedure for the diagnosis of hepatic steatosis and iron deposition in the liver is histopathological examination of tissue biopsy, but the procedure is invasive and other non-invasive techniques are desirable. The aim of this study was to evaluate the diagnostic values of magnetic resonance imaging (MRI)-based proton density fat fraction (PDFF) and T2* value in the assessment of hepatic steatosis and iron deposition, respectively, in various chronic liver diseases. Methods: This was a cross-sectional study of 196 patients between October 2015 and October 2018. PDFF and T2* value were estimated by the 6-point DIXON method. Each patient underwent MRI and histopathological examination of liver biopsy. Brunt classification used in histopathological examination classified steatosis into four stages; from S0-3 while Berlin blue staining classified iron deposition into four grades. MRIs were processed for measurement of PDFF and T2* value.   Finding: The amount of iron deposition had no effect on PDFF (1.9% for S0, 6.5% for S1, 13.9% for S2 and 22.3% for S3). However, T2* value decreased with increased severity of steatosis even in the absence of iron deposition. T2* values were 24.3 ms for grade 0, 17.6 ms for grade 1, 11.9 ms for grade 2 and 5.2 ms for grade 3 in cases with PDFF of <10.6%. Liver fibrosis had no effect on PDFF and T2* values. In cases with severe iron deposition, steatosis had little effect on the T2* value. Interpretation: MRI-based PDFF and T2* value correlated with histopathologically-determined steatosis and iron grades in various chronic liver diseases. In mild iron deposition, steatosis may influence the T2* value, and thus careful evaluation is required using the 6-point DIXON method. Funding: This research was completed without any government or non-government financial support. Declaration of Interest: Hiromitsu Kumada has received honoraria from MSD K.K., Bristol-Myers Squibb, Gilead Sciences, AbbVie Inc., and Dainippon Sumitomo Pharma. Kenji Ikeda received honorarium from Dainippon Sumitomo Pharma, Eisai Co., Ltd. Yoshiyuki Suzuki received honoraria from Bristol-Myers Squibb and Abb Vie Inc. Fumitaka Suzuki received honorarium from Bristol-Myers Squibb. Norio Akuta received honoraria from Bristol-Myers Squibb and Abb Vie Inc. All other authors declare no conflict of interest. Ethical Approval: The protocol was approved by the certified clinical research review board of Toranomon Hospital (approval number #641-H/B).