Comparison of liver iron concentration calculated from R2* at 1.5 T and 3 T

Purpose R2*, a measurement obtained using magnetic resonance imaging (MRI) can be used to estimate liver iron concentration (LIC). 3 T and 1.5 T scanners can be used but conversion of 3 T R2* to LIC is less well validated. In this study the aim was to compare 3 T-R2* LIC and 1.5 T-R2* LIC estimations to assess if they can be used interchangeably. Methods Thirty participants were scanned at both 1.5 T and 3 T. R2* was measured at both field strengths. 3 T R2* and 1.5 R2* were compared using linear regression and were converted to LIC using different calibration curves. Pearson’s rho and Intraclass Correlation Coefficients (ICCs) were used to assess correlation and agreement between 1.5 and 3 T LIC. Bland Altman plots were used to assess bias and limits of agreement. Results All 1.5 T and 3 T LIC comparisons gave Pearson’s rho of 0.99 ( p < 0.001). ICC ranged from 0.83 ( p = 0.005) to 0.96 ( p < 0.001). Biases had magnitude of less than 0.2 mg/g dry weight. Conclusion Agreement and bias between 3 and 1.5 T-R2* LIC depended on the method used for conversion. There were instances when the agreement was excellent and bias was small, indicating that potentially 3 T-R2* LIC can be used alongside or instead of 1.5 T-R2* LIC but care needs to be taken over the conversion methods selected. Trial registration number Clinicaltrials.gov NCT03743272, 16 November 2018. Graphical abstract