Quantitative susceptibility mapping in combination with water-fat separation for simultaneous liver iron and fat fraction quantification

PurposesTo evaluate the feasibility of simultaneous quantification of liver iron concentration (LIC) and fat fraction (FF) using water-fat separation and quantitative susceptibility mapping (QSM).MethodsForty-five patients suspected of liver iron overload (LIO) were included. A volumetric interpolated breath-hold examination sequence for QSM and FF, a fat-saturated gradient echo sequence for R2*, a spin echo sequence for LIC measurements and MRS analyses for FF (FF-MRS) were performed. Magnetic susceptibility and FF were calculated using a water-fat separation method (FF-MRI). Correlation and receiver operating characteristic analyses were performed.ResultsMagnetic susceptibility showed strong correlation with LIC (rs=0.918). The optimal susceptibility cut-off values were 0.34, 0.63, 1.29 and 2.23 ppm corresponding to LIC thresholds of 1.8, 3.2, 7.0 and 15.0 mg/g dry weight. The area under the curve (AUC) were 0.948, 0.970, 1 and 1, respectively. No difference in AUC was found between susceptibility and R2* at all LIC thresholds. Correlation was found between FF-MRI and FF-MRS (R2=0.910).ConclusionsQSM has a high diagnostic performance for LIC quantification, similar to that of R2*. FF-MRI provides simultaneous fat quantification. Findings suggest QSM in combination with water-fat separation has potential value for evaluating LIO, especially in cases with coexisting steatosis.Key points• Magnetic susceptibility showed strong correlation with LIC (r s =0.918). • QSM showed high diagnostic performance for LIC, similar to that of R 2* . • Simultaneously estimated FF-MRI showed strong correlation with MR-Spectroscopy-based FF (R 2 =0.910). • QSM combining water-fat separation has quantitative value for LIO with coexisted steatosis.